I have it. I've played...two hours of it, maybe? It's really damn cool, but I haven't gotten around to playing it any more recently.
I give due warning though: it's not all that easy of a game to just pick up. It's an RPG that actually has a mild amount of difficulty in its combat system. But it's still extremely fun, and has a very unique soundtrack, visual style, etc. The combat is the most unique thing though. It requires heavy use of the stylus, so be careful about making scratches.
Overall though, it's one of the best games out for the DS.
22 medium-jumbo frets, 3 mini humbuckers, 2 single-coil pickups, and 6 steel strings of pure sex.