It's a F2P (free to play) game, where you have GP and Zen (to get zen you have to pay money), however paying real money just gives you a boost in experience and get weapons more easily, therefore no one has a real advantage over the other as you can get all the same things by just playing the game (that's why it's cool, obviously I don't pay anything myself), and you have a quite fast gameplay (not as fast as UT, but faster than CoD and other popular FPS, that's for sure).
Also, it has a huge plus: no camping.
I mean, you can try camp, but is worthless in this game, since they have their own "wall hack" of sort to speak: a visor you can turn on which you can see all the players locations and orientation (enemies or not).
However, while you use it you cannot shoot, plus you can only use it for a few seconds at a time, and the longer you use it, the longer it takes to be usable again (which means, once you activate it, then deactivate it, you can only use it again after some time, until it fully charges up).
You can customize pretty much everything (weapons, equipment, character, logo, etc), take other players weapons ingame, buy other weapons/hardsuits/stuff in stations (never with zen, with the points you earned so far in the current match) ingame for the current match, the headshots are pretty awesome, and the game is overall balanced (I had no trouble to take out a level 9 player being a level 1 myself).
Plus, each player has a bounty on their heads, for each and every kill you do without dying, your bounty rises, and you can get to levels like "high threat", "warlord", etc, and once you kill these players you get more points than killing noobs for instance, which is equally awesome.
The game is still in open beta (meaning it still has a few bugs, nothing you can exploit though, just some annoying things), and has DM, TDM, CTF, DOM and KOTH (king of the hill). All of them are team based gametypes except DM.
I strongly advice who has a reasonable enough machine to handle it, to try it out (it takes a long time to download and install, but it's totally worth it imo).
http://blacklight.perfectworld.com/
If someone happens to try it out, my name in-game is Feralidragon, and I am generally either in the US-East server or in the EU server (they have 3 of them, EU generally goes down a lot lately so I started playing in the other one instead).