I haven't been able to wear out a PRII on the back as I pick up road crap and puncture the tire. I do still have the front PRII up front with 10,500 miles on it, maybe half worn.. The PRIIs worked fine in the rain for me (and it rains very heavy here in Florida in the wet season).
I currently have a PRIII on the back and its performed well so far (I really can't tell any difference between the II and the III).
The only thing I don't care for with the PRIII is all the little rain grooves (which of course helps in the rain). The reason being, its a bitch checking the tire (I had a very slow leak-turned out to be the internals to the valve stem) with all those grooves, the PRII, piece of cake checking it.
Once I wear out, or pick up crap, in the rear of this PR III, I'll likely go back to the PRII..