What? Why on earth would any man with any sense want to cheat on me??? Oh wait, two did - but now I think of it they didn't have a lot of sense :P LOL one was pretty spectacular in his ability to cheat as we were in an open relationship at the time :P Now that was a shock! Generally speaking the emotions went something like, hurt, feeling betrayed, incredulous, very disappointed and disillusioned with the person concerned...
I do think though that that said I would be able to discuss it with the person, to hear them out, find out their reasons and reasoning.. trouble is in situs like that by the point they have done what they have done it's too late to discuss and they feel defensive and not much into talking..
On a wider scale I don't necessarily think that cheating is the end - well unless the one who has cheated has decided they want to move on.