If I may suggest, there can be no real commitment as long as she is still married to you. I think that's part of the attraction for some of these folks. They go for a married person because they want no commitment and it is insurance that there can be none.
Good points Sleeper, and thanks for your experience in the matter.
Back to the original question about confrontation. In my case I did a lot of snooping (email and phone records only). She found out as I blabbed to a mutual friend (a woman who was a long-time friend of hers) who told her that I was monitoring her. Anyway, prior to finding that out W used to call from time-to-time and mention getting together (up until we sold our home in late June she would come over and spend weekends).
My point is that my snooping might be considered a form of confronting them. Regardless, since she found out she has gone further away.
Me: 48 Ex-W: 45 M: Nov '96, together since Oct 93 Bomb: on 10-yr anni - Nov '06 OM Separated: mid-Feb '07 Divorced mid-July '08 One daughter - 28 XW living w/OM