When somebody asks me "What should I install on my Windows Mobile PPC / Professional" phone (well, they never ask like that, but you know what I mean) my default answer is always Spb Mobile Shell. It's a great all-in-one customizer app that gives you a lot of the most-wanted features (weather, nice thumb-able interface, and some good eye-candy) in a single, simple package. It looks like Spb Software House has just updated the sucker, adding a ton of requested features:
Professional layout for Now Screen
Spb Menu customization
Now Screen as lock screen
Easy pinning on Today
Integration API for third party programs
I'm a big fan of the menu customization and the API - it means that Spb shell is starting to look like a great platform that will be able to give you access to stuff that's not included by default by Microsoft on your device. Bravo, Spb.