I've never had a partner that couldn't achieve orgasm, so anything I am bout to say is purely speculation.
First, I think it might make me feel a bit put-off to not be able to make him climax :ziplip:. I don't know why that is, and his "problem" might be just that... his own problem, but I guess I feel like it's a shared responsibility to see that each other orgasms.
Second, I would hope the guy in question has a good sense of time, or is of the mindset to not keep thrusting away in order to try and get off. I am sure some have this idealized notion of sex forever, but that can hurt, a lot. The limitless stamina of one, doesn't mean the other is immune to fatigue.
Truth be told, the thing that sticks out most would be sex without having to deal with the "cum where" question. :newangel: