My 2c: Ask an amateur musician what they think of the site (ideally ask several). If they all say 'wow', then consider it. If they all shrug & say 'I can do this on [say myspace] easier' then don't.
The reason is that people are unwilling to criticize something as harshly, so the scale of approval on doing some market research really goes from 80% approval to 100% approval.
Kudos to you for figuring this out on your own.