New PRL is 51716. Check your PRL here: Menu, Settings, About Phone, Status.
My wife's Eris was dropping calls on the old PRL, now the signal is still on the low side, but signal is steady and shouldn't be dropping calls with the signal strength she is getting now.
For a majority of people you could never update your PRL after the initial programming and you would be just fine. Heck, you could manually program your phone and NOT have a PRL and still be fine.