While I've only had my mini for about two weeks, I ended up installing Win7 RC on it about 5 days ago. I don't see what there is to complain about. It runs just as fast as or at least very close to Windows XP and has many of the benefits of Windows Vista (better security, built-in indexed search, better organization). The battery life seems pretty good as well. With the "new" Intel GMA500 driver, aero graphics can actually run surprisingly well.
Keep in mind that all I really do on this thing is listen to music, open about two or three tabs and write the occational e-mail and/or letter in Microsoft Word. (which is what netbooks intended purposes are anyways.)
I might put XP back on here; but considering how MS is offering $49 currently for their W7 promotion - I might just stick with this release candidate and upgrade when the time comes.
The only thing that does suck is that I can't stretch the display to 1024x768; which isn't that big of a deal; but was a nice option to have.