Ah, a new, nice and juicy format war has broken out during the Olympics with NBC using Silverlight and the BBC using Flash.
Now, it's difficult for me to make any kind of comparison since I still haven't managed to geospoof the NBC service (yet..); NBC are claiming around 250TB of video a day served, which I make to be around 4 million viewers. Despite serving a much smaller population at lower data rates, I hear that the BBC rivals this delivery, perhaps showing that internet TV viewing is more mainstream in the UK, or simply reflecting the success of the UK Olympic team.
The Silverlight installation is far more painful than Flash installation, but otherwise the technologies seem neck-and-neck.
Frankly, the user doesn't care about the format, they care about the experience, which is good news for Silverlight, which has a way to go to catch up with Adobe's ubiquitous product.
However, the Olympics might be high profile, but the real war will be fought on the Macs of web development companies and they will, inevitably, use the tools they have used for decades. And those tools come from Adobe. Silverlight might be a nice alternative for the VB devbase, but this is a war Microsoft lost a very long time ago.