What you are basically doing when you are playing Floatris is that you are playing eight Tetris games at the same time. With the Z and X keys (woe if you have a QWERTZ keyboard) you change channels, with the numeric keypad you maneuver the piece in the active well. Of course, it starts out slowly; but then, there are difficult, non-tetramino pieces right from the beginning.
I think that Floatris can help you train your reflexes very well; I can't say that it's very much fun to play, but YMMV.