I've put about 10 hours into it and it's quite fun. You can have up to 6 players at a time, you get the maximum quite often from my experience too. There are two modes, deathmatch and co-op boss battle; personally I prefer the latter. Deathmatch is what you would expect, but you can also play as a lot of enemies and npcs you encounter during the main game. Co-op boss battle is where it is at IMO though, where you face off against a boss in an enclosed area, not disimilar to the arena battles in Monster Hunter. I found the online fun, but not worth solely purchasing the game for.