Good Thread. My two cents in that, like most things, it isnt as black or white as we'd want it to be. People & relationships (or marriages) evolve and chage over time. I do not think that I am the same person I was when my wife met me, and I know she is not either, and thats probably a good thing. For me, I have secrets that I keep from my wife and at the end of the day (provided they all follow me to my grave) we are both better off for it. Ignorence is indeed bliss.
To answer your question however, damn straight seeing an SP is cheating.
-S