The Xbox Rewards site is now live, but seems to be getting hammered as Xbox 360 gamers flood into the site to register. Right now, the only challenge available is the previously announced Old Spice Experience Challenge; this challenge runs from now until April 7th, according to the site. As previously mentioned, gamers will qualify for prizes depending on their Gamerscore level, earning anything from Xbox Live Arcade games, to Microsoft Points, to a full copy of Fusion Frenzy 2 for the Xbox 360.