Level 1 (Gamers who have an annual gamerscore between 0-4,999 at time of entry): Game Picture, Dashboard theme, Contra for Xbox LIVE
Level 2 (5,000-9,999 annual gamerscore): Level 1 Package, 100 Microsoft Points and a contest T-shirt
Level 3 (10,000+ annual gamerscore): Level 1 Package, 200 Microsoft Points, contest T-shirt and Fusion Frenzy 2
In addition, Old Spice will give Level 1 and 2 the gift of experience by upgrading their Rewards Level for 2007.
Not a bad deal and given that it's free and all. All you need to do is hit this site and sign up.