Choices are good. Personally I'm semi-interested in taking advantage of this new ability. I'd like to try out a PvP server again, but I'm sick of releveling.
Still, it's true that it's harder to level on a PvP server than PvE. I've done both several times and I have little doubt of this. This is a bit unfair to those who leveled on PvP, dealing with the harder leveling for the benefit of open PvP at 70.
How about a compromise? Only allow PvE->PvP if the player has at least one max-level character on a PvP realm.