After having tried my hand on it, it's a good game, but it really lacks something to make me play over and over.
I don't know what it is exactly. But I cannot get into the game. I don't have the "Yeah i have won !" when I win, and I feel like it's pretty much one-sided everytime. Also there's no way to balance the teams within a match... And it's just not fun to fight for 5 minutes knowing that you can't do anything because of the skill difference.
I also don't like at all the design of the maps - especially when there is only one way in. Then the entire offensive team gathers somewhere before the entrance and nothing much happens for a couple of minutes.
I do get some fun times here and there, but I feel like it's too parse compared to the dull/boring times where you need a very good synchronized team to capture the point, and that's not going to happen any soon.
And I think this is the big negative point for me : in TF2, even if my team is losing hard, by picking the right character, it is possible to push forward the team. Here in Overwatch, the characters feel both overpowered but also useless when played alone.. You need at least someone else to push your team, but it is so unlikely to happen that you feel hopeless.