Very original take on a classic...
... but it lacks in a couple of areas. First off, the plain white background and the size of the pieces and the block in general was a bit straining on the eyes after several playthroughs. Maybe increase the overall size of the game window and enlarge everything a bit, and do something other than plain white for the background. And while its not completely visual, some sound effects / background music would add to the experience as well. You could do something yourself, or browse around the audio portal (I'm sure there are many artists who would contribute a song to this game for due credit, and you could even find a remixed version of the old school tetris track).
The next issue that I think is a problem is the next piece window that is a staple for tetris players, and it's missing in this game. In a game like this, not only would a next piece window help immensely, but also an indicator as to which side the next piece is coming from. Once the block builds up to a respectable size, it's easy to lose track of which side the next block will be coming from.
In tetris, the best play you can make is obviously clearing 4 lines at a time for a tetris. In this game, I wasn't sure if that same aspect existed. One of the main reasons was because of the nature of the game, it is just hard to build a block with one column missing and wait on the bar shaped piece to knock all the lines out. The other reason is because of all the awkwardly shaped pieces. I'm not sure if you originally tested the game with the 7 standard tetris blocks before deciding to add the larger and more complicated pieces or not, but I think the game would flow a lot smoother with only the standard tetris blocks, and would also make clearing more lines at a time for more points a more achievable goal.
All in all, it's a clever concept that's a little rough around the edges, and could use a couple audio and visual tweaks to really make it shine. I think with a bit of effort and the input of some good NG users, you could really turn this into something great.