Criticize me, please.

I sent out queries two days ago, and already I got a response! Sadly, it was a rejection. I'm fairly certain that he didn't read much more than the first few sentences of my email. Maybe I ought to take a look at those again and try to improve? I know there's usually no time for agents to explain why they aren't interested, but man I wish they would. It's impossible to objectively look at your own writing, yet it's so difficult to get an educated opinion. Writing seems like one of the only professions where people are out seeking criticism and can't get it!