Chris Sells and Ian Griffiths (authors of Programming Windows Presentation Foundation) have put up a pretty sweet article: Top Ten UI Development Breakthroughs In Windows Presentation Foundation

For all of you who keep asking me what’s so cool about WPF, this article gives a quick but thorough summary of the advantages that WPF brings to GUI programming vs. Win32 and WinForms without bogging you down in a lot of syntax or examples.