Frankly I think what put a lot of people off Gwen was her cheating on her fiance, feeding him retcon pills to get away with shit, and then still marrying him while she was secretly pining for Jack.

I think she actually turned out more interesting over time - but gawd,it did irritate me. It's not even the cheating per se. It's the dishonesty with yourself in acknowledging what you want and letting others suffer for it.