Nothing brand new under the sun, but nontheless a very good arena-FPS with nice ambientation.
The mechs are of three classes: light, medium and heavy. Every mech has their pros and cons, so it depends much on your play style. The CRT-Recruit, the first mech you receive, is a pretty good medium mech, and many will master this first free mech instead of buying a new one. You improve by buying pieces and with the mastery trees. The mastery trees can only be lvled by winning points with experience, and the pieces can be bought either with meteor (cash) or hawken (earned every game) points.
You must consider the game is still in beta, so many thing will probably change, but taking into account what's already in the game, it's pretty good and fun; it deserves that you test it and make your own opinion about it.