Looks like there is now a viable PUSH mail solution for WM5. Basic PUSH mail functionality can be added to the built in Messaging application through this utitlity. It's not a full blown Chatter replacement but it gets your email in realtime. Check it out:

http://www.vgsmail.com/ppc/

Discussion board:

http://forum.xda-developers.com/view...3613&start=300

The developer needs to add attachment and HTML viewing support but that should only take a few more days. Those that are using it seem to love it!

Looks like it could be the next best thing to Chatter on WM5!