I've played Lost Planet many times before, and it provides a great online experience. Unfortunately, it's lacking in players for two reasons. The game didn't sell too well, and also, Capcom re-released Lost Planet last year in the form of Lost Planet Colonies: the same game but with new multiplayer content, the biggest flaw being that original and Colonies players can't play together.
I'd keep away from this version and go get Colonies. If you're still unsure about this game, there is a demo available on the Xbox Live Marketplace, and there's even a multiplayer demo on the PlayStation Network, which gives an excellent preview of the online part. Make sure you get the game cheap though, because Lost Planet 2 is coming out this year!