Sam Gentile enthuses about the availability of the CLR on the Mac. Another thing is that Mac users, like PDA users, appear to be more willing to support small/Micro ISVs. Whether that would hold true for a Silverlight (i.e., non-native) UI, I don't know. But maybe I'll buy my first Mac since the F/X on which I learned Smalltalk circa 1990 (?).