Even knowing that the faces had to be oriented correctly, I could have sworn at first that the game was punishing me for pieces I had positioned correctly. When I played a second time, it did seem to be me that was screwing up after all! Having said that, I did find that some pieces came to rest a whole row above others, and that this was quite disorienting.
Good fun, and a nice twist when it plays back the song at the end. I only wish that the "wrong note" noise was a little less annoying - even when I managed 95% on my second playthrough, every wrong note still really grated. :)