I will admit that I tried CO when it first came out. Everyone with whom I was playing CoH at the time had already made the jump, so to have people to play with, I followed suite. I signed up for three months, after which I did not renew, and went immediately back to CoH, not really caring if anyone from my group followed me back, or not. There were some isolated things about CO that made me go "Hmmmm.....wish we had that in CoH", but at the end of the day, a newer graphics engine could not take the place of everything else that CoH had going for it. The costume/character creator, sidkicking, exemplaring, and the whole team dynamic. Add to that that it just felt a little more like a game over there, rather than a community like CoH felt.
Perhaps that last part is my own supposition, but the fact remained that I never let my subscription to CoH slip, and I came back as soon as I had given CO a decent chance to win me over. I did not leave again until just before the end, when I knew it was going away. I could not bear to see it go offline for the last time, and by that time, most of my gaming family had moved to SWTOR, so it kind of softened the blow. I have played SWTOR ever since, but as much fun as I have had with it, it has always been a pale substitute for the game I really wanted to be playing all along, and look forward to playing again.