I have only played one game of competitive mode. With the kind of internet connection that I have right now, I don't want to cost not only me to suffer penalties, but also my teammates. Once I move out of my parents' house, I should be good to go. But from everything that I've seen and heard so far, I think that the best decision they made was the one hero per user.
A friend that I play with said that they fought a team of Bastions and Torbs and it was just a waste and not happy that he lost because the opposing team just decided to do that. I'm glad that they gave Ana more bullets to her gun and I think they gave her like a speed boost or something, she feels really fast when I shoot consecutively. I've also noticed that people barely play Hanzo after all these hitboxes got toyed with. Now he's like... useless. And McCree, well, I don't think I need to say anything about the changes with him. I'm playing a lot more with him just because he's really freaking fun, and I want to work on his ultimate timing better as well. I rush in with it too much.
I would like to play competitive, but right now I just can't with the internet I have :/