I'm no fan of Vista. It's Bill's version of a MacOS. But folks were making the same cracks about XP vs. Win2k when it first came out: bloatware, resource hog, excessive graphical demands.
Once the hardware catches up, Vista will be an "acceptable" OS for the masses. That's how it's always been - a leapfrog struggle between hardware and software. But people only notice and complain when the software demands leap ahead of what the existing hardware population can support.
This time next year, XP will be left only to hard-core enthusiasts like Win2k was. Hey, I'm still running Win2k on a couple boxes.