I had a sprint TP on Verizon for about a month. It kicked much butt. I'm in Salt Lake City and Verizon coverage is really nice here. Anyhown, I deactivated my TP after having trouble from a rom that messed up some settings. I cannot re-activate my TP on verizon. I went to a Verizon store and they called in to make a request to add my ESN to Verizons list of acceptable ESN's. But I will have to wait a week before I know if it's a go or not.
Check this thread for updates about my status and others.
http://forum.ppcgeeks.com/showthread.php?t=61926