well I've had a few different reoccurring issues that make me delete the data.img and then do a TB restore on a fresh boot.
1. Repeated force close of apps
2. Get stuck in the boot process (stuck on xdandroid loading screen indefinitely or stuck in loop before the break in the boot sequence.) occasionally restarting and running haret again works.
3. loss of signal (just an X on the bars cdma w/sprint), even with reboot, disable/enable airplane mode...
4. turn off the phone then maybe 1/4th of the time gets stuck in the boot process (problem 2)
it's usually one of these problems every 2-3 days. I run android all the time, and usually spend an hour restoring with TB. still love it though