it's the only game in town AFAIK.
I've been kicking the concept around, but can't get past first base on the tagging. The way genres have splintered, and re-mashed, there's no way to describe anything except by instrument.
But even that is fraught with peril. What about synth loops, or arpeggios? And drums? Geez, I have to manually go through hundreds of sounds to make a simple song.