"As you've probably read, here and elsewhere, Windows Phone 7 constituted a dramatic shift for Microsoft. For this release, we decided that the core principle would be about delivering outstanding phone based experiences to end users. This principle guided everything we did, and was the basis for all the prioritization decisions that were made. It meant in many cases we had to focus, and not do as much as we've historically done in a single release, (focus has not been a strength of ours), but the things we did, we wanted to be outstanding."
If you're still kinda leary about going to Silverlight versus the native controls you've had access in the past for performance reasons, this short blog post might help ease your mind and give you a starting point to see if it really is as bad as you think (Who knows, it might not be!). If you've already jumped head first into WP7 development, you may still find a gem you've missed.