I've been writing a Silverlight app at my job for the past 8 months. I don't feel like Silverlight has given me any kind of productivity boost. I actually find Silverlight to be rather heavyweight and slow going, especially RIA Services which is boilerplate central.
I may have a bit of a "grass is greener" outlook, but I do feel my productivity would be higher with a web framework such as RoR. Especially if I was just as good at Ruby/RoR/JS as I am now at C#/Silverlight (I've been using .NET professionaly since its debut)
Then don't use Silverlight. My point wasn't to use SL per se. It was to use the best tool for the job. If you're most productive writing in 6502 assembly and then writing a binary rewriter to convert it to Logo, which you then compile to Javascript, go for it.
I may have a bit of a "grass is greener" outlook, but I do feel my productivity would be higher with a web framework such as RoR. Especially if I was just as good at Ruby/RoR/JS as I am now at C#/Silverlight (I've been using .NET professionaly since its debut)