The killer features I see with Silverlight is it's ability to run javascript four orders of magnitude faster than the current average browser. Firefox 3 is apparently taking Adobe's ECMA script engine which kicks the speed up a few notches, but for browsers on the market, this is amazing.

The other one that makes me giddy is the fact that Silverlight can control the DOM outside of its shell... and I can code in Python.

I doubt that it actually runs JS four orders of magnitude faster. It may run JS 2-5 times faster, but 10,000 faster is very unlikely. I'd love to run some tests though -- is there a silverlight demo with a eval loop somewhere? (something I can type js into and see how fast it runs)

The video demo is pretty amazing. Sadly the plugin itself requires an Intel core duo processor.

Sadly, this is probably Intel's doing. They're always looking for new reasons for users to upgrade their processors. Case in point: Microsoft Chrome.