One of the coolest mobile-specific features is the latest emulator support. It can simulate common & problematic scenarios (battery life changing) and allow you to code/test for it.
Of course, mobile developers get to enjoy most all of the big ticket improvments to '08 and .NET 3.5. E.g. VB users get enhanced Intellisense in many more situations and they get significant enhances to build performance and IDE responsiveness. LINQ and WCF are big ticket platform features -- VB developers get full access to those features inside of mobile.
I'll ask a few of the mobile experts if they can pinpoint a few more specific features you might enjoy.