I don't know about you, but I'm planning multiple playthroughs. I want to find all the secrets, get better times on my chamber runs, listen to the developer commentary, listen to more Stephen Merchant, and check out the awesome action set pieces again. Not to mention the co-op campaign (which I thought you could play solo, but I could be wrong?).

That's way more than 8 hours.

There is director commentary? That's pretty cool. That for me that is more of a hit or miss. I've enjoyed it with some games, but not all.

An early video of the coop shows puzzles requiring two people. Though they may have added some AI for people who want to play through that without another person.

My friend and I sat down to play the co-op at about noon or so. 8 hours later (minus a lunch break) we beat the final puzzle, feeling very satisfied with ourselves.

Aside from some iffy bits with trying to find places to attach portals, we enjoyed the game the whole way through.

No AI available for the co-op, two people required. They do a great job of requiring you to work together to win, though.

It's a shame there is no AI for the co-op campaign as like Left 4 Dead I would much prefer to play it that way.

Also I noticed after playing only a half hour or so that Portal 2 took away my control, even for looking around. That's the first time I recall that happening in a Valve game.

Lol, Ill just buy it when the price drops for the PS3 version... Use the code keep the book and then sell it!

Yup you can do that in this area at any local game shop with console games, Like if you sold tiger woods 12 without the online code you would get the same price as one without a used code.

Something tells me it would probably be very difficult to make an AI partner for Portal that doesn't suck.

Some of the levels for the co-op campaign would have been impossible to do with an AI the way I did them (not sure if there was another way).

Plus, the biggest plus of playing in co-op is having double the brain power, surpassing areas where one of you just has a mental block on the right way to do it.

You could probably attempt to play co-op solo-ish if you wanted by trying this:
http://forums.steampowered.com/forums/showthread.php?t=1847904

Something I haven't done yet. I've still got a long way to go before finishing the SP campaign I bet.

I just bought the game (PC) and haven't even opened it yet, but the topic of the co-op missions has me wondering... do you think you could play the co-op missions solo, playing BOTH players alternatively? I've got two PCs here side-by-side.... just wonderin'...

Or maybe you'd have to buy TWO COPIES to have discs for both machines (those weasels!)

You wouldn't need the discs, the discs with any game that requires Steamworks are just shiny coasters. As they don't work without the key, and if you have the key you don't need the discs. However, Portal 2 co-op would require 2 copies of Portal 2 as far as I can tell.

I considered doing that with the Amazon one. $20 game credit along with the $55 price effectively making it cost $35. Could probably have gotten at least $30 from Gamestop, though I've heard they give $40.

Best contemporary game i played in a long time.
The story was just madness and the end genuinly great.
Played it through yesterday within about 10 hours,
well, 11 but i got up every now and then etc.

Here is what pissed me off:
Could have done it in 9 or less,
if it wouldn't have been for the stupid confusing ways between tests in "old aperture".
Was also the only spot where i needed help.
http://forums.steampowered.com/forums/showthread.php?p=21930755#post21930755
I was there before but it was around the bloody corner,
which could never be seen at any point. What a stupid design decision.
Great game though. The room with the singing turrets is a instant classic.

It's not a first. Episode 2 did it as well, if I recall correctly. Episode 2 was also the first game to use non-first person-PC cutscenes (in the intro).

I found the first Portal to be overrated and I heard Portal 2 is even easier - not good. I breezed through the first one, beating it in three hours and a few minutes including one time where I got stuck because of an oversight.

So if Portal 2 does indeed take just 5 hours for those like me who find the logic easy, ... 45 euros? Seriously? Even with coop (which traditionally less than half the people will use) it's not enough. Not to mention coop for such a game is going to be annoying because it's not like L4D where you can join a game and just play - once you know the solution, you know it so where is the fun in replaying it? Or what if someone joins up who has played it before and is now replaying it, who will tell you the solution. Honestly, this is not well thought out unless you can make it so only people who haven't played it can join in.

Then it looks like we have to wait for the Chistmas sale. I share your opinion. I don't care how great the game is, I wait for a price drop or promo if it gives me only 5-10 hours gameplay.