You'll either love it or hate it.
I enjoyed playing Electroplankton, but I really don't like the online-only aspect of it's availability. That being said, the only way to know if you'll like it is to play it. This is hard as many people aren't so willing to part with the $35 just to try it, and only get $9 at GameStop for it if they don't. My mom ordered it for herself, and didn't like it. Granted she was expecting a game, I told her like 100 times it wasn't really a game... I took it to both my jobs, and people who were fans of Nintendo or into making their own music enjoyed it. People who didn't understand the "purpose" of it, or no interest at all in making music thought it pretty much sucked.
I leave the decision up to you as to which category you fall into. Though I recommend if you fall into the Nintendo fan/ music maker category, get it soon. I would imagine there is a limited number of games out there floating around as it is only available online at the moment...