Mechwarrior Online is a big, massive yawn. Once you get over the cool factor of controlling what feels like a legit heavy mech... it has very little else going for it. There are two game modes, and they're almost identical. There are several robots, though quite honestly the only real difference is that they're broken up onto four weight classes. Weapons are of little variety, shooting things isn't much fun, and because you're piloting a big tub of fuck, you can't really dodge anything. You've got a chance if you're piloting the lightest mech to circle around enemies faster than they can turn to shoot you, but beyond that it's all about praying that nobody decides to target you. Like any other multiplayer game, as soon as someone has you in their sights or targets you, they get tunnel vision and there's little if anything you can do to shake them off in this game.
I think a good comparison is Team Fortress 2, but only if everyone was a Heavy and you can only walk around with your chaingun revving(which makes the heavy walk slow). It's really not much fun. I wish they'd make an Armored Core Online.