I'm having frequent reboots too since the first run, but I configured Exchange for first.
Deleted Exchange profile was far more stable but rebooted once while trying to scroll in settings.
Deleting everything was not working for timeout like Exchange gmail mail service (while calendar and contacts work) and any sip service (can't make it register) the device is stable but not enought to survive more than 2 hours.

Anyway haven't tried heavy usage yet, just configuration.

My details:
Living Italy with 3G Wind SIM (should be 64k)
Firmware 1.2009.42-11