As a single player game when it came out, it was a fun thing to spend time on. You needed to be in a quiet place for the voice commands to work, which might not be feasible for a lot of people.
I still carry it around with me when I show off the DS's features to folks. I named my dog Otogi, after my favourite Xbox series, and he is a breakdancing ninja. I don't actually play it much though, I haven't even done a lot of the competitions. I just taught Otogi a bunch of cool tricks and left it at that. I tried to teach him to bark the 'Final Fantasy Victory Theme' using the piano, but that wasn't working too well :P

If you have some extra money to burn, I'd say it's worth picking up if you want to show people the DS's unique features. It's probably the best game for doing that right now. However it's not something that a regular gamer can spend a whole lot of time with. If money is tight, don't worry about this game. It was good when it came out, but there are better things to spend your money on for the DS now.