nope During gameplay, players may earn ribbons, which correspond to things like getting the first kill or taking your revenge on the enemy that has been deemed your nemesis. From what I played, it didn't seem as comprehensive as Halo: Reach's medal system, but does offer some extra recognition of notable feats during play over Gears of War 2.
Over long periods of time, players may earn medals, which have different levels of completion. This is similar to Halo: Reach's commendation system. Players will be rewarded for milestones i.e. 'Get 20 headshots', 'Get 100 headshots', etc. That isn't a real example, but you should get the point.
Unlocks will be handled not by raw experience and leveling up, but by completing specific challenges. Every weapon in the game besides the Snub Pistol will have its own unique execution. Players will have to unlock weapon-specific executions through this challenge system. While they do not directly affect gameplay, players will be vulnerable during these executions. If you choose to use lengthy finishing moves, expect to earn more points than players that utilize shorter animations.
Other unlocks will include player variants like 'Thrashball Cole' and custome skins for starting weapons. Epic originally looked at including a perks-type system that offered gameplay bonuses, but decided it wasn't right for Gears of War and would be too difficult to balance properly.
Read the rest of our Gears of War 3 coverage.