I'm missing only 2 little features, but they would help a lot working with SA:
1. Global Search - search all the files of the project.
I need this all the time and WinGrep helps me out a little...
2. Switch automatically from design-view to code-view when opening a controller.
And the other way around also ofcourse...
Besides of that SA 3 beta is practically not useable for me - it very very often shows "The application is unresponsive" for 10 to 30 seconds. Clicking OK or Cancel terminates SA.