I use whatever is available (Preferrably Linux, tbh).
I quite like Vista and the way it handles things as oposed to XP. The memory management is a big step ahead (If you wish to know how it works, read the next paragraph). I can agree that Microsoft DID focus on the wrong things, such as Aero (which is eye-candy more than useful, and it's just a marketting tactic to be honest). However, overall I don't mind vista. Mind, both operating systems have their flaws, which is innevitable - if humans aren't overall perfect, can they be expected to create something perfect in the first place?
Okay, so the Vista memory management system is what I like about the new OS a fair deal more from previous versions. Speeds up processes considerably, and increases overall effectiveness. Microsoft has implemented what they call "SuperFetch" (If the name is wrong, excuse me, I haven't studied the matter for a while), which basically automatically loads the memory of commonly used processes automatically, and fills the RAM that isn't being used for fast allocation. After all, unused RAM is wasted RAM.
Hence, SuperFetch can profoundly increase load-times for commonly run tasks, which saves a lot of time in many cases. I happen to have a 3-year-old laptop which has some of the worst specifications I've seen since the early 2000s, and yet Vista runs on it as smooth as XP could ever be (if not, faster). It has automatically detected what resources I have, and enabled and disabled such features as needed. In example, Vista automatically detects my laptop can't handle Aero very well (due to the crummy Intel video card) and doesn't install it.
Leading back to my original statement, I don't care solong as I can use it.