Hearing and feeling a guy lose control is very hot. Listening to moans, gasps, dirty talk and breathing rate increase and feeling his muscles tense and quiver is definitely a turn on for me. Nothing artificial or way over-the-top, but if it's sincere go for it. Also shows that the guy trusts me enough to be completely himself and share that part of himself with me which makes the experience better, and it helps me learn what he likes.