I've been riding a pair of P3Rs and granted they do wear fast, but I haven't had any problems with them. The first race I did on them was day 1 on the tires, and had 15 miles of nasty gravel on the course and they did get small cuts in the tires but no flats.

That being said I wouldn't recommend them for a training or commuting tire. They are marketed as a RACE tire, so I wouldn't expect the durability out of them that you get from gatorskins or armadillos which if you're worried about flats you should train on. So what if they're heavy? It is that much more of a boost on race day when you take them off.