This isn't the tactical shooter you're looking for *waves hand*
Disregarding the gamebreaking bugs (which will probably be fixed), the horrible UI (which you can get used to) and the generally unfinished state of the game, this just doesn't feel like a tactical shooter at all:
The AI is absolutely dreadful in co-op, flopping between 360 noscope and OfP's CQB AI's mentally incapacitated little brother. They hardly respond to any cues like supressive fire (or in some instance, fire), they don't take cover, they don't defend the objectives, they don't seem to care about breaching charges or flashbangs...
The map and game-round design are not conductive to tactically approaching the objectives: the words non-linear design were thrown around quite a bit in the run-up, but really the problem starts before you even get to the map: there's no level designs, there's no planning phase and you can only choose between two entry points but there's no part where you can choose to approach the buildings or areas because you start straight in the middle of the action. This means that to have a chance at choosing a logical, tactically viable approach because you'll have to rely on knowing the map from having played it 73 times beforehand. As far as the non-linear spiel goes ingame: there's corridors and you have 2 (!) staircases to go up and down. But still, every level looks like it was designed with a gamey mind, resulting in a bathroom-between-the-kitchen-and-the-dinner-room kind of jumble.
Player movement seems pretty odd. You want to run around with your sights up all the time, which is very slow, then you have the option to run a bit faster but you'll never have a chance to get your sight up should you be contacted, and then there's a sprint that'll clip you into a doorway should you try to use it for a bang and clear. And while I know that it isn't necessesarily part of "gameplay", the other players movement animations make it look as though they have a sever case of stiff neck. Furthermore, using the grenades is not a very intuitive experience: takes quite a while to whip one out, you have to hold it down for a significant amount of time to get a full force throw and its hard to place them correctly. Maybe it's just my twisted view of tac shooters, but I find a lot of flashbangs through every door a core aspect of gameplay.
Of course, the bugs don't help: nonreaction to flashbangs, open doors everywhere (I mean, the best part of a tacshooters is agressive room entry right?)
All in all, I had a playtest with three guys, and after about an hour we decided to quickly install SWAT 4 and had a better time.