Incidentally, I picked up the new Chris Sells / Ian Griffiths book on WPF last week:
If you want a slick and pain-free introduction to WPF, this is the book to get. It's based on Whidbey Beta2, so it's pretty current. Chris's style, as usual, is conversational but information-rich, and he carries you along easily from subject to subject. Highly recommended for all skill levels. Okay, you'll probably want to be pretty comfortable in the .NET environment and UI control development.
Chris just posted an interesting endorsement on our internal Avalon discussion board. The gist of it that for all the grief he's given the Avalon team, he loves Avalon. He wouldn't have authored half a book if he "didn’t think it was absolutely the most amazing presentation stack [he’d] ever laid eyes on."
High praise indeed. WPF could be one of the Next Big Things.