If you're replacing the rotor anyway, then beat the living crap out of it from the back with a sledgehammer. That pops it right off after a couple of blows, and badly mars the rotor surface in the process. Remember to smear a little anti-sieze on the hub pilot hole of the new rotor before putting it back. (And of course smear the anti-sieze on the hole in the alloy wheels if you have them!)

As a marginally-related aside: I have a 2003 F250 4x4. I assume the front rotors pop off the same way, i.e. no need to undo wheel bearings or anything? I think mine just have pad material on them which I'll try to clean off, but if they're actually warped then it's replacement time.

Duncan