I stuck with XP for a long time, only switched over to Vista a few months back when I got this shiney new laptop I'm using right now (I love my laptop). I've had a couple of crashes of various kinds, I've had the older games not working issue as well, and the constant "This action needs your permission" "Are you sure you want to give your permission?" can get on my nerves if it happens sixteen times in four minutes, but apart from that I like it. I prefer it over XP.
While I usually cover my desktop with immense sedimentary strata of screens for - usually - at least four to six different programmes at a time (and two or three on average per programme) (and yes I'm a stickler for British English spelling), I do appreciate the sidebar a whole lot. The clock is handy, below that is the headline reader, below that are three notes (I have insane resolution) and finally I have the currency converter at the bottom. While, like I said, I don't use it very much, it is in my eyes a very useful addition and while not really a necessary improvement over XP, it is handy to have around.
I'm also a fan of - I know, I know - the visual style. The transparency and "softness" of the screens appeals to me, and since I decked everything out in a dark green tint the overall effect is pleasant.
One more thing I like is how you get a little preview pop-up if you hover the cursor over an item on the taskbar. Like the sidebar, it's not a necessary improvement, but it is handy.
I can't speak for Internet Explorer, since the only site I ever visited with it was the Mozilla site, to install Firefox.
It took a little getting used to the new file explorer address bar thingy, but now I find it very handy, and actually much more useful than the old style. This, in my eyes, IS a necessary improvement.
Of course my view on the subject is inherently biased since my laptop is beefy enough to run it without lag of any kind and run fairly new games (one-two years old, tops) at a respectable graphics level (which isn't really all that useful to me since I mostly play older games

), so I can't speak for the memory hog aspect that's apparently such a mark on its record. Overall, I find Vista to be much more pleasant to use than XP. That said, I think I'll probably stick with Vista until Windows 7 is due to be replaced, like I did with Vista and even XP (I used Win98 for a looong time, my first XP comp was SP2 already), to get the best results and the fewest headaches.