I am just starting to look at Silverlight. I'm impressed what some are able to do, but not impressed - generally - in the "development velocity" story around Silverlight. XAML isn't brain surgery, but editing it manually seems like a step back from the flexibility of WinForms.
It might be the future, but it isn't the present.
To that end, a very cool Silverlight game was recently posted by Roger Guess. It's pretty cute looking. It's pretty fun to play. And it's very addictive. Check it out:
http://www.playmatter.com/DefendStuff/