Don't buy it now.
The community is very small. It has been down to 20-30 players average for 8+ month, and the player number, or whatever left from is, is steadily going downhill. Chances are, if you are unlucky with timezone, that you never see more then one lobby going. Community was driven away by numerous patches making game unplayable, now player count is steadily going downhill. It's EA, but even then disregard for the players is outstanding. Here are recent player numbers:http://steamcharts.com/app/265590
Patches, most of them, completely ruin the game, so the ones who persist play the role of testers because developers don't bother with testing themself. Some patches bring back the bugs that were "fixed" ages ago. One day you might find that the game crashes just before victory screen, or sometimes in the game's final and most incentive moments. Or that some weapons are broken. Or skills. Or something else. After players enjoy some time those patches, they roll out hotfixes and prepare for the next patch. There is "testers" beta-branch but it is often more outdated then stable one. Those patches driven away a huge chunk of community.
Game engine is a complete mess. Because of hand-made engine this game has poor networking: lags, teleports, everything that could desync WILL desync, skills not working, weapons not dealing damage, ....
The other problem is lack of collision. I bet you didn't see that in promo videos, but if you play this game once you would see that monsters are moving one through other. So fat bosses (big and slow monsters similar to wc3 abominations) could be kited to form one mega-boss with dozens of hands just because it's easier to kill them all at once. Same with any other monster type. It's not just monsters, marines walk one through another too, rockets and bullets fly through walls, but they collide with lamp posts, trees and ,sometimes, empty space above the road. It requires tons of work to fix, so devs aren't going to bother with it until after release.
Graphics is also very bad. I don't care much for it, but still bad textures+no lights+red clouds make awful appearance. That's not going to change so think about it too.
If this game is so bad, why did I play it that lot? Long time before, game was well balanced and there were more players. Some of them are still playing now, but most people that play now have ranks of "Elite commander of force commanders that command elite space marines". This game has 25 ranks, with the 25th requiring 2.222.222 exp, while per game you get, 2.000exp (average game)-6.000exp(perfect game, very rare). And if you think this is grindy, know that they are going to add 10 more "prestige" ranks. Yep, the ones resetting your exp counter to zero. With 24 million exp to go, this game could be an infinite grindmill.
Anyway, i have played with most of them so we are able to overcome whatever buggy ♥♥♥♥ developers introduce. Also, it was quite fun back then, noone knew a thing about the game so the only way to find out was to try it. And there is some special kind of fun in doing complex missions together and pulling out extremally tight situations! It could be achieved in any other coop shooter though.
And of course you could look for positive things in other reviews. It could have been a decent tactical coop shooter, was the developing process not screwed that much.
Now, for every new player wandering in lobby, there are 6-7 super force commanders, who know everything in game. Sometimes they kick you for having wrong layouts, but no wonders there, if you take any layout different from the "canonical" one you die, and fast, even on easy. If you have any doubts about it, new players have rank 0 which says "ready to die". And the gap between ranks is really huge, those who achieved rank 25 are 2 times more durable, inflict 40% more damage, have much more speed and health\armor regen.
That is, loadout variety is very limited. For 4 out of 8 classes there is only one good weapon. Since every mission spawns Upgrades items, which boost specific weapons, there is even less choice what to take. Well you could take whatever you want, but if you don't use those, you die. 1 upgrade for every weapon and 2 upgrades for generic assault rifle(GAR), so with those 4 heavy classes taking all the cool upgrades, medic, demolition and recon have a choice of GARs. Every class has skills that are overpowered and skills that are ♥♥♥♥. So people tend to get kicked if they dont take OP skills and take ♥♥♥♥ skills. Mind that OP skilled are unlocked only after you play some games (up to 20) with that specific class.
Current game session lasts ~60min, the survival mode. You have a map with supplies scattered around and should do your best to loot items and complete missions while waves of monsters try to kill you. There are 3 maps now but people play hardly 2 of them ,most stick to the default one. 3 more are coming. They are going to have some mad unlock conditions so i doubt that they are going to get played much.
If you re still with me, and still have faith in this game, wait for release, the moment developers stop ♥♥♥♥ing around with untested patches, the moment when all content is added and working, the moment more people play this game, the moment there is more then one game going.