Interesting concept, it felt a bit slow and physics were a bit wonky i think could be challenging and fun after you polish this a bit. I do have to say the music was not that great i think in this case no music would have been preferable or at least a mute button.

This heavily reminds me of the old flash game Avalanche (http://www.avalanchegame.org/). It's a cool idea, and I like the spin with the tetris blocks. The gameplay is a little too slow, and blocks often rotate when they land. You can fix this by locking the rotation about the up axis on your rigid body.

Texturing the blocks more like tetris blocks would have also been a nice way to upgrade the experience.