Just to throw my 2c in.
I've been running Win7 on my main/home/media PC since January (the first public beta - 7000). I upgraded to the 7100 release in July.
This is a computer that runs our TV with media center, shares our files through the house, and is my main PC. It's always on, and I'd be surprised if it's been rebooted more than 5 or 6 times since going to 7 (mostly service packs).
In my opinion, it's still as smooth as it was on day one. In saying that, I'm especially aware of how software can bloat the system, and whilst I wouldn't say I restrain myself from installing things, I am a little anal about checking what a program will install before going ahead with it. No toolbars thanks, no updaters if it can be helped (so Foxit reader instead of adobe, sigh google, fine keep your updater), etc. I just think it's prudent.
I do have the firewall enabled, and I do run Microsofts new virus scanner thing (Security Essentials). I personally think a firewall is not something optional, and that it's a good idea to have some form of virus scanner (even the new MacOS checks downloaded files if I understand right?).
I don't worry about viruses though, at least not the ones that will destroy my computer and data, I think those are few and far between these days, on any OS. I don't think that windows is targetted because people hate the platform either. As far as I can see, the reason why someone wants access to your PC is to use your computer as a zombie to spam/ddos, or to steal your data/WoW account login. The fact that Windows has the greatest presence on the web makes it an obvious target... As MacOS grows it will find itself increasingly targetted. If they've learned from Windows' lead, they might be able to nip it in the bud a bit (the download checks is a good start/example).
Also, about this 'wait till SP1' sub conversation, I'm in the 'It's good enough now to make the switch' camp. It's been in very wide use since January, and I think it has proved itself along that timeline. You might even consider the beta/RC as the first release(s) and the retail release as SP1, if that eases any minds. Yes, it is a decent chunk of change from the beta to the release.
The only problem I have had was user ignorance... I installed a video codec pack that wasn't ready for Win7, and the way codecs were installed changed from Vista. Yeah you need to watch for some things like that, but for the most part keep your eyes open when you're doing things and you'll be fine.
I also run Win7 on my HP TX2 convertible tablet/laptop. It has a multi-touch screen and a digitizer pen. Windows 7 is fantastic on it, and I highly recommend if you have a touch screen that you pick up 7 for it. At work I find myself reaching out to press Ok on dialog boxes on the screen, only to catch myself halfway. Touchscreens are definitely the future, and I'm most definitely going to be an early adopter if a dual multitouch 'touchbook' ever comes out (like the Asus concept). Thinking about how awesome it would be just blows my mind, and yes, I think Windows 7 would power a touchbook perfectly.
(I wonder if one could replace the keyboard of a mini with a mutli-touchscreen...hmm would lose the tactile keys but, touchscreen!)
Sorry if the post came out a bit long winded, but I think I covered everything I wanted to