SpykeZ knows whats up. ProjectI.N.F. is the one I'd recommend for some action. A lotta fun, and seems like there is a good number of people playing. Cestos is also good, but definitely check out ProjectI.N.F.
Yeah, still Beta, but fun regardless. It'll be nice to see what they add in the meantime. Technically I'm pretty pleased, the game runs smooth and it's quick and easy to get in and out of games.