Currently running Vista 64-bit on my desktop and XP on my laptop, it works for me. Yes, I know Vista is a horrible resource hog, but I refuse to upgrade to any new M$ OS until at least SP1, it takes that long to get the bugs out.
Whether or not it's the "best", who cares? I could certainly imagine ways that *ALL* operating systems could be better. It happens to do what I want it to do, better than any other OS I've tried, therefore I use it. When and if that changes, we'll talk.