Another distinct problem I have is with alt-ctrl-del responsiveness. One of the great advantages of win2k over previous versions was how reliable the task manager was. Even if explorer froze, alt-ctrl-del would (almost always) work, the task manager would always come up. You could then kill explorer, start it again and things would be as good as new (or at least good enough to try a clean reboot...).
Vista? Not so much. I imagine the disconnect between the window manager and explorer now causes that to be unreliable. Sometimes the alt-ctrl-del menu comes up, sometimes it doesn't. Sometimes the task manager comes up, sometimes it doesn't. So pretty much anytime either explorer or the window manager have problems (which is likely given the novelty of the change) you get to hard-restart your machine.
Which is perhaps why the repair/restore stuff which seems new is pretty bad ass.
Speaking of badass, the foggy translucency rocks. The problem with translucency in every other window manager I've seen is it's clear (or shaded), making the background patterns of text/color interfere with the translucent window. The fogging effect in vista makes the color contrast less severe, and the translucency doesn't interfere with use. It doesn't look much different from other window managers, but in practice it's exceptionally better.
It also looks like file version control is built right into the OS. I haven't toyed around with it, but that seems like something that will really come in useful later.
Microsoft mail (the new outlook express) seems pretty cool. It's got built in anti-spam/phish stuff that caught stuff that my provider's (conservatively set) spam-assassin missed. Not much new, but seems much more responsive than OE.
Nothing much more yet.