I agree with Cyn. I have no doubt that once the dust settled, that marriage was doomed. No delusions of happily ever after for me, despite the closing scene. I personally still really enjoy this flick. I watch it almost every time I stumble across it on TV. I love watching the cheater being tormented, and Michael Douglas plays it extremely well, IMO. I love his look of helpless terror every time he almost gets caught. Yes, the ending unsatisfying, but even now, every time I watch there's a tiny part of my brain that believes he'll finally get what's coming to him this time.
Agree with Alex that the film probably didn't stop many people from cheating, and it was rather silly to think that it might on any large scale. However, I think the style of film making and the story itself are very much emblematic of the 80s. One thing I appreciate about it is that it's an adult story starring actors who looked like real adults. I feel like we don't see this enough anymore. I imagine if this were remade today, it would have a cast of actors who could pass for high-schoolers, or they'd even rewrite it to be about actual high-schoolers. I can't imagine Glenn Close and Ann Archer, with all their 40yo fabulousness, would be considered for sexy leading lady roles like this if it were being cast according to 2012 standards.