It actually sounds like ridiculous amounts of fun. When you activate Bullet Time, one of several special "Burst" powers in Max Payne 3's online multiplayer, only players in your field of vision are slowed. What does that mean? It means you better damn well make sure no one is behind you when you activate it.
Imagine running across a map seeking opponents, only to stumble upon a slow-motion ballet of blood, bullets, and shirtless men in jeans. This is going to be glorious.
Update: Rockstar informs me that the line-of-sight is per-person, so if you see a teammate or enemy in Bullet Time, you'll be in Bullet Time as well, at least until you break line-of-sight. Even more entertaining.