It's pretty good - one of the better music index services I've used. Others here have commented on a few small issues but overall it seems well executed.
However, is this really a viable business? I assume you intend it to be, based upon your description of it being a startup, but please correct me if I'm mistaken. Otherwise, I'm afraid I'm going to have to piss on your parade a little bit.
I have considered developing something similar to this in the past, but I've always stopped myself - simply because if it becomes any sort of success and is seen to be either (i) taking in revenues or (ii) encouraging others to develop similar services then the RIAA will give the slightest of gestures.. a wince of the lip perhaps.. to direct a battalion of lawyers to march upon your place of business and annihilate it with a bombardment of 4,000lb bombs stuffed with subpoenas and the internal organs from children and puppies.
Although many (including myself) argue that what you're doing is probably legal, it is not really open and shut - the RIAA would argue that you're encouraging and cooperating in the acts of copyright infringement. It's going to cost you a fortune to defend yourself.. and even if you manage to generate enough revenue to successfully defend yourself once, they will keep coming after you time and time again, from many different angles.
If the CoS can sue the IRS into submitting to its demands for tax exemption then the RIAA can shut down your little operation. The law can be cruel if you can't afford it.
If anybody else (with legal training) can enlighten me then I'd love to have my doubts assuaged.