Sorry if this has already been posted, but I figured I'd stick this in here.
I just bought the game a couple of days ago since it was only $5 at Blockbuster. I tried playing while connected to Live, and it kept freezing at the main menu. According to several sources (most of them posts on this board, among other places) the issue is because EA's TOS, which is supposed to pop up at that point, isn't on the disc or something similar. The fix is to download a demo for a game that came out at around the same time as this one, the most commonly used one seeming to be the first Army of Two game. Start a multiplayer game of any type, accept the TOS there, and quit out of the lobby and then the demo. Fire up Mercs 2 and you'll be able to play as normal when connected to Live. --- RIP Eddie Guerrero 1967-2005. He will be missed.
World of Mercenaries is an upcoming free-to-play FPS MMO by City Interactive that developed Sniper: Ghost Warrior and is working on Sniper: Ghost Warrior 2 currently as well. Built on Unreal Engine 3, it aims to present stunning graphics, silky controls and skill-based gameplay.