In my opinion (and I'm not saying it's worth all that much) we're in a situation analogous to the time when folks were discussing the relative advantages of the 80386 vs the 80486 (remember them? before Pentiums).
I know that was a hardware example, but even with software I think the PC industry often times spoon feeds small incremental improvements to users with a lot of advertising and little substance, attempting to maximize income using a ramp down pricing scheme. As we all know with the perspective of hindsight, the improvements from Win95 to Win98 to WinME were purely incremental, at least compared to the major leap that WinXP represented.
Of course, you could argue that Vista is the next leap. I don't think so. I think MS has lost its edge, lost the momentum and the mystique. I also don't think they "get" the big picture (i.e., communications, entertainment, security, changing demographics and governmental realities). Personally, I'm playing a wait and see game because I think we *are* ready for a quantum leap, but I'm not sure whether it's going to be application delivery by Google, or true computing/entertainment integration, or broader broadband/wifi. And I do *not* want to waste my hard earned money on a bunch of tiny incremental steps, I'd rather buy at the middle of the price ramp than at the top of it, and I don't think the industry wags know how it's going to shake out either (but maybe I should be more humble, huh?)
My 2 cents worth.