I played the Open Beta, and wasn't really feeling it much.
Especially without a team to work with.
It really is a Team-Oriented Game, during beta, Zerging was useless and pointless, and it wasn't even that much fun. The initial map got really old, really fast.
The demo on the other hand, feels quite solid. They slowed it down a bit, made the hit detection a bit better, and it feels alot smoother than it was before. Even zerging is more fun, especially as Strogg with a Hyperblaster.
My only gripes are that the game feels WAY too linear to complete objectives. There's no "well, maybe I can go this way, sneak in, steal this point" so on and so forth. It's just a real tug of war, point for point, push and shove game at the moment. Sad because it had so much potential.
Although, I do have to say to those who think it's too fast. It's based on QUAKE. Quake 3 Arena anybody? It's not Battlefield or Rainbow 6, it's the Enemy Territory version of Quake. I like the pace myself. It's got a good speed, I don't always run outta stamina when running, I can get from point A to point B fairly fast. I hate games that are so slow it always feels like you're waiting, just to die.
All in All, it's an Average Team-Oriented Shooter.