So you've developed with Silverlight and understand its strengths and weaknesses in comparison with Flash/Air? I haven't done much Silverlight work but as someone who has done a decent amount of Flash work in the past, I thought it was a really solid approach. It certainly seems superior to the other alternatives in the context of developing for a phone platform (Windows Phone 7, or whatever that is called).

The DLR is used by IronPython and IronRuby. It's not the basis of Silverlight but it is what allows you to write apps in python or ruby.