just because i'm obsessive about this i can't help but chime in
i've been using a system of very broad genres, with another system of subgenres that are somewhat broad themselves.
for example i have the Cure as
rock
goth; new wave; sad
my sub genres are in checkbox (list) format so they are pretty easy to slap onto an album. the advantage as i see it is i can search a lot of different ways, and get cool mixes of different styles by selecting "goth" i'll get some electronic, pop, and metal in with the Cure, but adding "new wave" i pretty much just get the Cure, Siouxsie, etc.
anyways point is i agree with blgentry and i personally have no interest in any source telling me what genre or sub genre any of my collection is. good luck and have some fun with it. i'm about 70% done my collection now and i'm happy i've gone through the process as it's a very personal categorisation
and finally if you do use a program and it's returning good results, post it here!