A few comments...
If you have used Vista, the chances are you will think Win7 is great - you've already had the pain of learning where stuff is, and hopefully cottoned on to the new way of working (ie, pressing Windows on keyboard and typing CV to update you cv document etc). You've already come across UAC, and hopefully understand its benefits, and also know you should NEVER disable it (if you do, your ego is bigger than you basic computer knowledge).
If you are coming from XP, having skipped Vista, then you've got a bit of learning to do - a lot of stuff is in different places, and it takes time to learn to automatically use the search box on the start menu. You also need to learn that running as a computer Administrator does not necessarily run you as an admin - one of the best security thing MS has done to Windows, and one thing that catches a lot of XP'ers out.
IMHO, Windows 7 is an improvement on Vista, which itself was a massive improvement on XP (which was always rubbish due to the compromises to get the Win9x line into it (which is why W2K often multitasked so much better), SP2 improved the matter, but look at the uproar that caused as it broke poor apps/drivers).
If we had gone straight from XP to W7, I guess people would hate W7, due to the changes and to UAC. Also, the new driver architecture would mean all the drivers would be immature and not as abundent.
Windows 7 does have excellent driver support - in most cases, if there is no specific Windows 7 driver, a Vista one should suffice. That is not always 100% the case, as some driver manufacturers can't even get simple things right. 64bit still isn't 100% covered on drivers, despite Microsoft's insistance that any WHQL driver has to come in 32 and 64. Older printers seem to be a common one. I had a problem with USB - Serial adapters under Win7 64 (and Vista 64).
Lastly
NEVER EVER EVER upgrade an operating system. ALWAYS rebuild it from scratch.