Responding to profiles for us is about the whole package. A couple who is physically attractive to us (not perfect, but definitely fuckable), who is looking for an experience similar to what we want is our basic criteria.
If their profile is humorous or gives clues to their personality (and we like it) it also makes us more interested in responding. It also makes it easier to contact these people - we can reference something in their profile instead of sending a generic "hey we think you're good looking wanna fuck?"

Big Tits :)