Marble Blast just came out a few hours ago for xbox live arcade. Nice graphics and liquid smooth frame rate. (I heard it got 85 fps then they optimized the engine and it went up to 300 fps not sure what the final fps ended up being but its definetly above 60) Pretty fun game, I only have the trial right now but I' ll probably buy the full version tomorrow. It plays kinda like Marble Madness did way back on regular Nintendo. Pretty similiar to super monkey ball. You either have to complete a course in a certain time, or collect gems then complete the course for single player.
For multiplayer everyone races to collect gems, as soon as all of them are collected more appear.

You control the marble with the left stick and the camera with the right stick, you can also jump. You can also do a marble blast, which if you can use to jump higher or blast other marbles away in mp. Your blast slowly recharges over time, you can wait till it is full to have a bigger blast. There are also a bunch of differnet power ups you can get and use with the right trigger like super jump, speed burst, big marble, gyrocopter and some others.

The physics are really good as you would expect for a game like this.

Uses the Torque Shader Engine, same engine I' m using for the Age of Muskets game I' m working on.