This game seemed like it was one of the most sought after when the private multiplayer demo was first released on Xbox Live. I say that because I watched the blur Facebook and Twitter pages. They were passing out beta codes through those two sites and they were being grabbed up quicker than a @MajorNelson Free Code Friday!
Now any Gold Member of Xbox Live can grab the multiplayer demo and give it a run. Blur has already hit retail shelves and I imagine after you try this demo out that you might just be heading out the door to grab the full version.
Game description from Xbox Live Marketplace page for Blur:
Blur: Powered-Up Racing. Travel the globe to beat the best the streets have to offer. Utilize an armory of Power-ups including huge bursts of energy, defensive shields, nitro speed boosts and mines to beat your rivals across the finish line. Blur features insane collisions, realistic damage, stunning racing environments, real world locations and licensed photo-realistic cars. In multiplayer Blur supports competitive game-play for up to 20 racers online and 4 players locally split-screen.