UGH! the opportunity?? don't we ALWAYS have that choice. its pretty much, free will. and my answer would be no.
speaking from personal expierence, i've cheated before, and it only made things worse within my relationship. I don't know why I believed that it would make things different or better or whatever... but i have a conscience and it just ate away at me... even though the dude was treating me like total shit. i still felt bad. looking back, it was just acting out on a lustfully sexual impulse driven by purely nothing. it was almost, pointless on all accounts.
I would NEVER do it again. It does nothing for me or anyone else. I vowed to myself, after me and the ex broke up (not because of my unfaithful ways) I would never do it again. I couldn't dream of doing it EVER again.
We all can cheat, but it's turning it down that makes you feel good.