It is off putting when you get no response at all, as you are just not sure if what you are doing is right for the guy or if you should do something different.
Just as disconcerting was the guy who kept saying 'oh, yeah, I'm cumming, here it comes!' and then didin't, about four or five times - then he said 'oh' (and I thought here we go again) but he said sounding unsure - 'I think i've cum' - well, what could I say to that?