I just noticed this thread again - very interesting commentary and subject matter. I have found the statistics to be interesting as well, even remarrying the ex-spouse (I have seen that happens anywhere from 6-18%, though for me the 18% seems high).
I have also seen that affairs typically do not last more than 24 months, and those marriages between affair partners end in divorce 85% of the time within 2-5 years.
Despite all these stats, I personally know of three people who left their M and married the affair partner. One woman has been with her affair partner 15 yrs w/3 kids together, another woman has been with hers 7 years and just adopted kid #1, while a guy I know left his W+3kids after ~ 13 yr M to cheat and then marry his secretary (10 yrs his senior and not a looker). I would guess my W has been living with her OM for about a yr, and I have phone records that would indicate a relationship going on 2 yrs (also uncovered another EA, possibly another A, and casual sex last summer while on a 'girls weekend'). On the other hand, I can not think of any reconciliations.
Regarding the casual sex with the estranged spouse, we did that for 7 months post bomb (5 of those she had moved out). It was great, and although I was suspicious I could not confirm OM until after we sold our house last June, after which there has not been more physical contact. There seem to be different schools of thought regarding this topic, and who knows which is best.
I am a little suspect of some sites that have a lot of un-named testimonials touting the return of WAS.
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