Avalon is very promising. No doubt about that. I can very well imagine how Visual Studio "Orcas" (the one to follow Whidbey) will add fantastic designers for creating stunning Avalon UIs. However, today, my first steps with XAML remind me very much of my first little baby steps exploring the Win16 API back in 1990 using Charles Petzold's Windows Programming book. Of course, it's all on a vastly elevated level and some of the controls are stunningly powerful, but putting together an Avalon app that actually looks good is pretty difficult right now. I am not complaining -- it's very early and I am happy that Microsoft lets me play with the stuff. I am just so horribly spoiled by visual design tools.
I figure that Avalon will create a lot of new jobs for designers. In fact, if you don't have a designer, your app will look really, really old, no matter how well you master the Avalon technology.
And I figure that I'll have to freshen up my math skills on trigonometry and linear algebra in a big way. Vector graphics is a very different ballgame.
Oh... and MSBuild does really rock the house.