Well it is fun but...it is not great
So after installing it and playing it for some time my first opinion of it was "AWESOME!" and that pretty much set the tone for the time I spent playing it for the first and second day. The thing is, this feeling does not last very long.
Killing large batches of creatures is fun and will always be fun ESPECIALLY if you play with friends. However it is not enough to keep you glued to this game for very long, mainly because you never actually feel powerfull. It is the feeling that is missing from this game, you know you are powerfull but you never feel it. Let me explain.
Serious Sam has you walk about plain-jane levels killing HORDES AND HORDES of monsters, you are litterally packed from floor to ceiling in monsters, the more players joining you the more monsters spawn and then it gets insane. The weapons you use hose down the monsters really easily and you feel the power, your screen shakes, the kick back is there and recoil is great. Hellgate london misses this and pays for it dearly.
The graphics are pretty, the lighting is pretty, the shadows are dark and scary. Some glitches like not being able to shoot down from a platform unless you jump on the hand rail, enemy shadows appearing on the roof from the floor above, occasional jittering corpses. All of this happens on the top of a line machine like mine so even if your hardware is good, the game still has major bugs. The levels are also too repetitious, same levels over and over just a different spawn spot each time. That is poor development.
However there are many classes in the game and you can be either sex for each class, the gear is plentifull and random and various, the customisation of your gear is pretty great but playing for gear alone is a little silly and pointless when there is nothing else to back it up.
Play it by all means and have fun, just have in your mind that it is a stop-gap game or something temporary until something better comes along, it will never be a great game but it really really had the opportunity to be. Shame really.