You know, if you look at the history of Microsoft Windows, there are some real advancements, and then there are some real duds. You have Windows 95, which was the starting point more or less, then you have Windows 98, which was a bit better, bit more secure, and became a real standard when the majority of America started breaking into buying PC's for home, then you have WinME, a total flop, then Windows XP, a real shiner.
Now, you have Windows Vista. I'm inclined to say that Windows Vista, was really nothing more than a skinned Windows XP with horrid performance. Really, there is nothing new or innovative. Everyone I know that is using Windows Vista is primarily using it because they want to play all of the new games with DirectX 10, which in my opinion is a big farce right now by looking at comparative screenshots with directx 9. The Crysis (PC GAME) community will attest to this, and defend this believe vigorously, as many of them are very upset.
Overall, I wouldn't bother with Windows Vista unless you're running the absolute top end of the spectrum PC with over 4 Gigabytes of ram an even then I'd still wait for the next generation of DirectX 10.1 video cards, because the current generation really isn't handling gaming too well in win vista. Aside from gaming, you have a lot of office workers wishing they were still on XP as well, or at least that's the gist I'm getting reading discussion on the web.