Jeff Prosise explains about one new feature of Silverlight 3 -
support for hardware acceleration.
In Silverlight 1 and 2, all rendering was done in software, which meant that the performance of complex animations and video playback depended heavily on the capabilities of the host PC. Silverlight 3, however, can take advantage of hardware GPUs. You can see this for yourself in Beta 1 and even measure the impact that it has on performance and CPU usage.