I thought the game was limited - the puzzles too easy, and after a while they're all the same. The challenge mode, while engaging for a while, doesn't have the lasting appeal, seeing as it's notoriously unforgiving, and uses set-pieces, so becomes a memorising game more than anything.
However, I just played the multiplayer mode for the first time the other day, and it's pretty awesome. It's as different formt eh other two modes again. Basically, you send over completed lines to your opponent, and the game ends when a player manages to send all of tehm to the other. So it's arace to send lines back and forth - you see the ooponents screen, so you can see exactly how fast and big a set they're sending over. Pretty neat.