I've been using Vista for about a week and absolutely love it. I really don't understand why people prefer XP, other than that they are used to it. Vista can do anything XP can do, XP can do some things Vista can do.
Aside from the fact that "it just works", which is an enormous fact, there are some great changes in accessibility. My personal favorite is the start menu. I never even use the menu, actually -- I just use the search. It's awesome to be able to hit the orb, type in the name of whatever I want and just launch it. No more digging through a start menu of 200+ programs.
Accessibility is improved in every conceivable way. The calendar, the start menu, explorer file viewing, gadgets, etc.
Have any of you tech savvy folks who hates Vista checked out the Resource Monitor? Task Manager > Performance > Resource Monitor. It's amazing.
Back to "it just works", as that's probably the biggest improvement... I first built this computer, plugged everything in (printer, keyboard, mouse, monitor, speakers, etc) and the Welcome Center pops up and tells me I need to install updates. I thought it was Windows Updates, but no, it knew everything I had plugged in and it had automatically found the drivers for them. My motherboard, videocard, sound drivers, printer drivers, drivers for my monitor... everything. It knew what model everything was -- even the printer, despite all the Vista/Printer trouble I've heard about, it knew the exact model of my printer before I did anything and it gave me the driver I needed. I check the box next to each one, click install and it installs all of my drivers all at once. When an updated driver is released, the Welcome Center lets me know.
This is an unnecessarily long post, but I consider it my love letter to Vista. If you don't want change, stick with XP, but Vista certainly isn't bad.