Big Tetrinet fan here, I used to play the modified version Tetrifast a lot(no new block delay) which is the same as this, you can lay blocks with speeds of 120+ ppm(pieces per min) depending on the keyboard repeat and initial delay settings(usually needs to be reduced). One flaw I see is there is only a key to turn the pieces one direction, and not he other, this should be implemented to increase speed of laying. Also, it would be cool to have customizable keys for those of us who don't use standard, I tend to use(may not be optimal):

down: drop, e/r : turn piece left/right, up: faster descent

Unfortunately very very few people play Tetrinet anymore, I wish you the best to revive what was a great game!