While the system will allow that ESN change the problem is that Verizon phones are setup to use different towers. Even with the PRL download they will use the wrong towers in many areas. Alltel phones will typically roam off of Sprint towers where the Verizon is going to try like hell to use a Verizon tower. If you were to use a Storm on an Alltel account in say IA it would potentially use the USC towers instead of Alltel in some areas.

I would avoid it if possible.