The Win7 RC (release candidate) is rocksolid!
On my 3y old portable is noticably faster than Vista. And it just runs smoother than XP.
I've now installed it on a brandnew iMac 24" (with the ATI HD graphics) @ 3.06Ghz and 4Gb ram... It's blistering fast.. It's a delight to run Photoshop CS4 and Lighroom 2! No hickups, no crashes (yet).. Can't complain at the moment.
And.. I know.. abusing an iMac for running Windows... It's just that I like the design of the iMac.. and can't find the software I need on OSX. So no flaming please :-)
The race for quality has no finish line- so technically, it's more like a death march.