It looks fairly well done. I prefer the random bag method of piece generation. Also, the movement of falling pieces is a little touchy--sideways movement can sometimes generate a double movement and sometimes no movement.
However, if you play around with the game on meatbrick.com a bit longer, you'll see there is more to it than a Tetris clone.
Yes - played a bit more now. Funny idea. Number 3 touched my heart. I don't know waht random bag is - I suppose it assures that certain tiles appear after a certain time?
The touchy movement appears when you repeatedly hit a movement key instead of just holding the key down. I optimized for holding key down to have a fluid movement (no delay at the start of movement like i.e. in your Tetris).
But it seems everybody is so used to this flash bug(?) that they keep hitting the buttons :(