I've got a free upgrade version of Win7 (Home Premium), and I'm wondering if it's worth upgrading from Vista, or buying a full version for a clean install.
Slightly worried that the upgrade will not work properly and I'll have to reinstall vista and then upgrade to Win7 without all the bloat that I've got at the moment.

Back during the open beta I installed 7 alongside an existing XP install, using 7's bootloader to switch between them, and it worked flawlessly. You'll only run into problems if you install 7 and then XP, and even then it can be resolved by reinstalling the newer bootloader.
If you use Linux or the like you can also add that to the 7 bootloader but it has to be done manually, so you might find it easier to install 7 and then reinstall the other bootloader over top.
Also, as others have said, don't even consider using the 32-bit version. If you find something that doesn't work (which isn't all that likely) you can run it via XP Mode which presents the virtualised program in a seamless manner (start menu shortcuts, free floating window, access to host files, etc.). XP Mode works for almost everything short of 3D games, so between that and the native compatibility you should be able to run just about everything.

Er, upgrade versions are literally no different from full versions except with the ability to upgrade. Microsoft doesnt exactly want you to know this...but yeah. I clean installed Win7 upgrade with no issues at all. Much cheaper. Go for that.
As for XP, why not use XP mode in Win7..
Definitely go for 64 bit for reasons Arkose said. I cant think of an issue Ive run into there.
Best of luck. :)

As I said, one of the programs I use for work has an extensive memory which I've taught it over the last year or so. That memory cannot be exported and it'll take a fair amount of time to reteach on a new install. So I'll be keeping my current XP install for work.

Oopsie. Very tired/long day.

No worries =)

The upgrade versions they sell to college students too. I had to choose which version to buy... but I got Win 7 Ultimate for $20 :-)
Rock solid. No reason to dual boot. (that I can imagine, anyway)
Wait. What? Why?
Does Aero cause problems with Source?

Really? Thats the version I have and I thought it had both. Oh well not like I'm ever going to use 32bit again...

Several of us have said there's no reason to dual boot... but that was before reading this line. When it comes to proprietary software like what I imagine you are using, all bets are off. In your shoes I would definitely dual boot.

So it seems the company I'm working for has decided to not bother upgrading their PCs this year after all because one of the companies they work with isn't bothering to upgrade either =/ So it looks like I need to find the full $450 myself if I want to upgrade this year =S.

And thats for the upgrade version or the full version? I can always pick you one up here if it'll be cheaper, could even get an oem copy when a mate orders his new psu sometime soon

That's the RRP for the full version. The RRP for the upgrade version is around $350. Perhaps I should see if Amazon.JP has a better price. The downside to Amazon is having to pay it all in one lump sum as they don't provide the option to pay in installments which means it's better to pay COD than to stick it on the credit card.
I suppose I could just borrow some of the money we've put aside for the children, they're always taking my money after all =P.
Edit: And yup, Amazon.JP currently have the full version for approximately $350.

You're only holding your children back by sticking with xp, you really have to upgrade, its your paternal duty!

I usually buy my OS upgrades from TigerDirect. They are cheaper because they are the OEM upgrades with limited support and return. You would have to confirm the upgrade is OEM but I'm fairly sure they are.
Here is a link for an example of one of their offers. I think they accept PayPal and I have always used a credit card . . . hope this might help with your search . . . =)
Edit: I was wrong this is the OEM upgrade . . . sorry =)

My kids don't even touch the PC =S But my wife has just informed me that we have to change our modem as the phone company is finally switching to a digital line. Apparently they phoned yesterday asking what OS we had, so I guess the sooner we upgrade the better just in case the modem is going to hate on XP.
The good news there is that my connection should become a "little bit better" (hopefully, a little bit faster) and the modem is equipped to handle fiber optics. The bad news is, we still have to wait another 18 months until they lay the fiber optics here =/.

Thanks, but: "We accept wire transfers only for international orders."
Will be a huge problem. Japanese banks are totally and utterly backwards. Trying to explain the concept of a wire transfer will be a long and pointless task (one I've tried before) and the chances of them actually doing it without making you wait 3 months and taking 90% of your money, near zilch.
Ah well. I'm resigned to having to pay MicroShaft's localised butt hurting markup.