We purchased two batteries from boxwave (Verizon Pearl 8230 Replacement Battery / Verizon BlackBerry Pearl 8230 Replacement Battery / Verizon Pearl 8230 Extended Life Battery / Verizon BlackBerry Pearl 8230 Extended Life Battery - ElectraSpan
The battery is AWESOME. Our doctors can go a full day and use barely half a charge (after making the usual power tweaks - screen brightness, bluetooth off, etc.).
The door, however, not as awesome. There seem to be slight gaps on both sides of it, and it doesn't quite feel snug. We had one phone that the battery seemed a little loose - when the phone is "slapped shut" the phone might reset itself due to the battery shifting slightly. Upon closer inspection, the battery casing/housing is slightly different in configuration than the stock battery...which may contribute to the shifting that we were noticing.
I installed a couple bits of foam tape (about 2-3mm thick) to the battery to help hold it in place):
1 small strip on the outward face top of the battery
2 medium strips on the inside of the battery door (which would also overlap the small strip applied to the battery). Be sure to make it so there is a bit of 'breathing room' for the battery.
This seems to have helped, but I don't have any long term details on that.
I'm calling boxwave today to find out if they know about this issue or if it is just this particular doctor after a "drop" incident.
Oh, one other thing to note - our phones are the 8230, but the battery door is for the 8220 - so a big black battery door on a silver phone.