Big supporter of Chatter myself. I call it the one app I can't live without for my Treo 650! No resets here! I have been running his betas for about 2 months now. One beta didn't want to play with Directory assistant. Everytime I was using the mapquest feature of directory assistant, and mail came in, it would reset. All I did to address it, was to turn off all accounts.
Chris mentioned snappermail, and
agendus pro might be another alternative.