The fact that Rhys is being cheated on bothers me a lot. He is a great guy and he has put up with so much shit from Gwen. Sadly though fandom is focused on the Jack/Ianto pairing so that is where the indignation falls off. Honestly, knowing Jack I would be surprised if he and Ianto didn't have have some kind of an agreement about having sex with other people. Jack's world view just doesn't fit with physical monogamy. Emotional, however, I can see especially since he knows this is really just another short term relationship for him.