Custom launchers seem to be the theme for me. Removing them has made a difference, but there are still occasional reboots occurring.
Also, I notice custom keyboards may be a culprit as well. Swype with the error tolerance increased and split keyboard with some customizations seem to bog the phone down occasionally and I'll get a reboot. I noticed it with the stock ROM, Broken Out, and Nitro's version 0.2.
Nitro did mention something vague about removing GoLauncher from 0.2 due to some reboot issue. Has anyone seen more detail on that?