I need some straight answers from Galaxy users first though. (Non Galaxy users, please do not respond.)

Artificial achievements have no appeal to me. I have some questions before making my decision.

1. Can I go straight to my game without being forced to see any adverts, either for other games or for other services?

2. Will it slow down my time-to-gamestart with extra loading of stuff that is not specifically related to the game I'm playing?

3. Can I opt out from remote servers recording details of when and for how long I play any particular game?

4. Will Galaxy consume any PC resources (clock cycles/memory etc.) during gameplay?

I'm genuinely interested in multiplayer, but I need to know the facts first. Please don't make this a Galaxy bashing thread.

Don't tell me how to live!

I haven't used Galaxy for a lot of multiplayer games, so it's possible that YMMV. Mainly use it for Dying Light events.

1. You can, AFAIK. The only way to know for sure is to try the games that interest you.

2. If it did, it wasn't long enough to notice.

3. When you load Galaxy, click on the gear in the upper left-hand corner and then click "Game features". That'll let you turn cloud saves, achievements, time tracking, overlay, and auto-updates off and on.

4. Any program will use system resources. I'm not sure how much Galaxy uses, though.

My 2 cents: Try it yourself. I am not trying to be funny its just that your questions are very specific and require detailed responses. I did try Galaxy once like a year ago. I have some screenshots somewhere. Do I remember everything about it? No, but I clearly concluded it wasn't my thing. From my vague memory:
1 - No
2 - Yes, as any program in the middle you will notice it, no matter it takes only a blink. I hated it launched and opened galaxy main screen just for a second to immediately start opening the game...
3- Don't remember. One of my reasons to try Galaxy was to test the time recording thing. It wasn't very accurate
4-Didn't measure it, but as in 2, yes, you notice something. For an accurate response you would need to measure an offline game vs. the same game through Galaxy don't you think?

Last but not least, probably asking on the Galaxy forum would get more participation.

https://www.gog.com/forum/general_beta_gog_galaxy_2.0

Best way is to just jump in and try it. This might be helpful as well: https://www.youtube.com/watch?v=U2KbK6BnOZE

Glad to see people who aren't stubborn and refusing to even give Galaxy 2.0 a chance! As for your questions...

1) Yes, 100%, no adverts for anything and you can still launch your Galaxy-installed games independently of the launcher.

2) I haven't noticed this, personally, not even on my laptop which is significantly weaker than my desktop. That said, your results may vary.

3) Unfortunately, I don't know the answer to this one. As far as I know, there's not an option for it but I may be wrong.

4) The only resources Galaxy ever consumes are the ones it needs to run.

I highly recommend it! It still has its issues and plenty of room for improvement but it has effectively replaced every other game client for me. I always use it for my GOG games and most other games unless I'm playing a recent, resource-heavy game (for which I only launch whatever client I need to play it). It's a great UI, has plenty of great features, no real spyware (though the telemetry is a little concerning, I do trust that CD Projekt is only using it to better the product). In general, it's definitely a really solid client and the bashing only seems to come from the people who insist that non-LAN multiplayer and optional cosmetics are DRM... which is to say, we can largely ignore the bashing.

Hi Boris mate.

Former client user here.
I used to run it, in order to test out download stacking and speed, store interconnectivity and cloud save recovery.

First of all, I want to say that even though download stacking is something you can do via the browser as well, when downloading Offline Backup Installers, through the GOG Galaxy client, all the download links for the split parts are laced into one overarching link.
Something that would be very useful, if it was also added to the browser-based site (perplexing oversight).

Secondly, I could not observe any download speed differences which could be attributed purely to the use of either the browser-based site or the client.

Thirdly, store interconectivity does not alleviate the burden of having to install any 3rd party clients to download and play licensed software (as expected). It is heavily focused in cushioning the first contact shock, of users coming from licensing platforms, primarily by providing a familiar, one button does it all , so to speak, client experience and secondarily by syncing contacts.

Fourthly, saves can be stored online (if you don't localy backup them), by running a game via the client, (for those games that are supported by cloud saving), but can be only downloaded through the client (saves can be downloaded as independent files) and are not available for download through the browser-based site (another perplexing oversight).

Last but not least, client downloaded game packets' signatures do not match the ones offline backup installers have, so any game installed using the offline backup installers, if imported to the client, will be redownloaded from scratch, no matter if the version is the same or not.
There are instances where download of large files can get stuck for hours and ultimately entirely fail, though incosistently, not as salvable as browser based downloads of split parts, due to the one link to download them all function.

Personally, a good offer, that I quickly and effortlessly realised I never needed, so by process of eliminating amenities, was shortly thereafter graciously discarded.

Now, to answer your specific questions.

1.Yes, as long as you set the starting page of the client as your game collection library or installed games library. In game launchers not included.

2.Yes, as long as there is a GOG Galaxy client update to be downloaded. Game updates are automatic by default, but they can be disabled via the client settings. You can still run the downloaded games through their executable located in their respective installation directory, skipping any client and game updates, unless it is a game that requires constant connection to online services in order to play (GWENT, No Man's Sky, e.t.c.).

3.Yes, as long as you choose so from the client settings. For any other data, vaguely collected or not, I kindly suggest to trust your network packet sniffer.

4.Yes, as long as it is running, it will withhold system resources. I mainly observed an increase in RAM consumption of 180-240MBs, as stated under the Windows task manager, under standard use, and it can be safely assumed that some amount of CPU calculations are being made to keep the threads of the client process running. Ultimately, the amount of system resources utilized, is related to the activity the client is performing at a given time. The more intense the activity, the more resources are withheld.

I hope you find this information helpful, while I suggest cross-checking it for yourself for an up to date impression.
Cheers!

1. Can I go straight to my game without being forced to see any adverts, either for other games or for other services?
You can setup your starting page to either way "Installed" or "Owned" Games. This will be ad free.

2. Will it slow down my time-to-gamestart with extra loading of stuff that is not specifically related to the game I'm playing?
Realistically Speaking - No. Especially with disabled Overlay any "Delay" in game launch should be around the 0.3-0.5 second ballpark and should not be measureable/noticeable

3. Can I opt out from remote servers recording details of when and for how long I play any particular game?
Game time tracking and achievements can be disabled from the Settings. Same for the Overlay.

4. Will Galaxy consume any PC resources (clock cycles/memory etc.) during gameplay?
Windows 10 here - Galaxy with Origin, Xbox, Epic, Steam, Amazon and Uplay integration.
5 Minutes after startup CPU usage between 0-0.5%. Memory usage 740 MB! (so ya noticeable effect on memory consumption if you have a larger library and use several integrations

You can always still install the games with the offline installers and only start Galaxy when you need to use any of the features. When you start Galaxy it would need to update your game library though, which could take some time, and it would also check for updates in your installed games (though I think those options can be disabled via settings.)

In any case, I haven't seen advertisements in Galaxy at any point.

I'm not a current Galaxy user, but I did try it for several months earlier this year. From my experiences:

1. Can I go straight to my game without being forced to see any adverts, either for other games or for other services?
Yes.

If you don't use Galaxy as a launcher and start your games from shortcuts then you won't see any ads at all.

Galaxy's default home screen does show "recommended" and "popular" games. But you can change the start screen to only show your library or installed games and you won't see any of that.

2. Will it slow down my time-to-gamestart with extra loading of stuff that is not specifically related to the game I'm playing?

Once Galaxy is running, games don't take any longer to load than without.

Galaxy takes about 5 to 6 seconds to load the first time on my system. If you leave Galaxy running in the background, subsequent loads are instantaneous. If you shut it down after each game then it takes a few seconds again to reload the next time you need it.

3. Can I opt out from remote servers recording details of when and for how long I play any particular game?

Yes. There are options in the settings menu to disable time tracking, achievements, cloud saves, screen overlay, auto-updates and all the "social" stuff.

Galaxy still sends some telemetry details back to GOG while its running. There is no option to disable this unless you block it at your firewall. Here's a list of the telemetrics that are collected: https://www.gog.com/forum/general/telemetry_in_gog_galaxy_20

4. Will Galaxy consume any PC resources (clock cycles/memory etc.) during gameplay?

When I disabled all the extra stuff mentioned above, I seem to recall it taking about 300MB RAM and CPU utilization was under 1% once it was finished loading. If you enable other features -- especially the screen overlay and chat -- it will be higher.

If you disable all its optional features, then it's not too unreasonable -- especially if you only load it when needed for multi-player functionality. I'm currently not using Galaxy because I don't require any of its features at the moment, but if I started playing a game that required it for multi-player I wouldn't be adverse to using it for that purpose.