Not trying to pile on, but I'm curious to what sort of feedback "nothing in there really caught our eye" would engender. A request for YC to look more closely? I mean, at some point these are qualitative measurements. Even if you had absolute knowledge, it wouldn't make things any better. Did the reviewer have a bad burrito for lunch? Is your name Bob and the reviewer unconsciously hates all people named Bob? Was there a great application just before yours, and even though yours might be acceptable, by comparison it didn't look so good? Were you the first ones evaluated (reviewers are notorious for rejecting early applicants)
I exaggerate, of course, but whatever reason you get I can guarantee won't be satisfying. I mean, you can go to the store tomorrow and pick up a huge stack of books on selling, which all boil down to "Sometimes you strike out for no reason at all. Keep trying" In a vain attempt to pump readers for money, some books give you a huge list of reasons for why you can strike out. I'm a firm believer in controlling all those factors you can -- wear the power tie, turn the temperature down in the office, sit in the proper locations in an important meeting, use body language and NLP, show instead of tell, etc. But I've never had a client say "You know Daniel, we really like your work, but gosh, those shoes are just not doing it for us". That kind of thinking is just grasping at straws. It never works that way.
Look at it this way: a couple of years ago I sent a business plan into a local VC group for their paid-evaluation service (pretty good deal for them, huh?). This time, for my $200, I got back a bunch of comments. What did they tell me? That the reviewers were idiots, that's what. And how exactly could I use this information? Except to be bitter, not at all. So not knowing when it's qualitative is a pretty good thing. As for me, I'd rather save my money and get rejected for free.