You have 400,000 people who actively use your product? I imagine a bunch signed up thru TC, and the initial press, but how many people use it day to day?
Around 40,000 uniques per day. So 10% log in daily? That seems reasonable for a site like this. I guess Facebook is at 50% but that's super insane rare.
Otoh Fandalism is kind of like LinkedIn in that I'm not overly concerned with user engagement -- it's more about building the database of users and content (so they can meet likeminded musicians, and one day I can launch new services that take advantage of the large database).