To clean install or upgrade? That is the question.
I have an MSDN subscription through my work so this weekend I downloaded the Windows 7 Home Premium 64-bit RTM. I own an ASUS G50vt gaming laptop. My wife owns an HP dv123 (or whatever the model is; can't remember). Both of them were running Windows Vista Home Premium 64-bit. I was debating whether or not to upgrade or do a clean install. I have a LOT of games on my laptop and my wife has a LOT of pictures and email addresses and such on her laptop. I looked around the internet and found LOTS of posts about always doing a clean install since you never know what 'sticks around' after an upgrade and you want to make sure that you are getting rid of everything.
Well, I went the upgrade route on BOTH laptops mostly because I don't own an external hard drive and didn't want to take the time to move stuff to one computer/install/move it back/etc. I'm here to report that the upgrade route went FLAWLESSLY. After it was done I checked all my programs and everything is working just fine. I checked my wife's and everything is working just fine with one exception. HP has that Quick Play bar that runs across the top of the keyboard and has buttons like Play, Skip, etc. We use it occassionally but not much. Well, as soon as you boot up her laptop and the OS loads you get a popup that says the HP Quick Play is not compatible with this version of Windows. Options are to find a solution online or run the program or cancel out of the window. I first clicked the 'Check online for a solution' button and it basically said that it couldn't find a solution. So, next I tried 'Run Program' and it works just fine. No problems.
So, long story short, the upgrade path (instead of the clean install path) is definitely a viable solution and worked like a charm for me on two different brands of laptop. And it is definitely a SWEET operating system. Supremely easy to find stuff and I can't wait to setup my 'Homegroup' which allows me to browse my wife's laptop while I'm on my laptop, and vice versa.
Have fun!