My husband is uncut, and I'm pretty rough with him because that's how he likes it. It drives him crazy when I nibble and pull at his foreskin, and I love the fact that uncut penises don't require as much lube.
He has a LOT of foreskin, and even if I give him a good long stroke from tip to pelvis, there's still plenty left to go around. So, I think it would take a lot to make his foreskin uncomfortable, like purposefully pulling it back too far.
I actually prefer giving head to an uncut man, because it's more fun. There are more things to do with foreskin.