I play it, but don't spend any amount of time in it though. It's fun to jump on, run a few missions, then jump off. If you like super heroes, it's your only choice. It's not terrible, but it's not great either.
Downsides:
It just gets repetitious fast, the attack chains are nearly the same every time. The enemies start to blend together, not much variance. There aren't that many zones (4 I think). The crafting sucks.
Upsides:
It looks nice. One server. Very large zones. Regular content updates.