Silverlight, ugh. That's reason enough not to use it.
I'm not so concerned about competition with Apple or Adobe or their technologies - more competition = good, bring it on - rather, it's more to do with Microsoft's semi-developed Mac products, partial commitment to the platform, and limited feature parity.
Firstly, was Silverlight actually done by the MacBU, or is it like WMP for Mac, which was developed by the nongs in the Media Player group? And how long will it actually last, before Microsoft loses interest and dumps the Mac version, to "consolidate their products and focus on their core apps" like they do every now and then? How invested do people want to get when Microsoft don't have a great track record in keeping things going? And how many Netflix features will be missing, types of videos will be unavailable, and options will be "coming soon"?
Color me skeptical, but that's my $0.04.