Windows 7
After a steaming pile of poo that is Windows Vista, looks like Windows 7 will be something that is done right.
Ok, to be fair, Vista has lots of new features and improvements under the hood. Now, I haven’t used them, but transactional file system, exposed low level APIs to get detailed memory/IO stats, etc. etc. sound like cool & useful stuff. The problem with Vista is that all those core improvements are out-weighted by inconsistent & slow UI and some stupid blunders.
Now, Windows 7 seems to be taking on two things: 1) performance and 2) consistency. Building on all the low level improvements done in Vista, and getting the part that is visible to the user right. Yay if Microsoft can pull this off. We’ll see.

Ow really? For me, Windows 7 is just same Vista with “improved” Calc and Paint :D
I have faith in Win7 but more faith in the incarnation of Windows after that. From the videos released a year ago showing off the Windows micro-kernel I think that Windows 8 will be a great step in the right direction.
@BadVista: I’d love to see how you tested Windows 7. Obviously you must have tested it to make the claim that 7 is just Vista with a better set of accessories, even before the public beta release.
But in the end I also know that 7 is just being released as an update to the 6000 series of builds, not built from scratch. IMO, it would be great to see Microsoft undertake an enterprise of the NT magnitude. Start over and do it well.
E. Luten.