I got my first rejection! And it was both exceedingly polite and encouraging. I feel, well, rather happy about that. It's entirely a positive thing.
I've only queried about 10 agents so far, and most of their websites said 4-6 weeks' response time, so I was rather surprised to hear back from anyone yet (or at all...) I actually hope I get more rejection letters in this vain, because it was at least semi-personal and friendly, rather than just a form. I appreciate the response, anyways, and it gives me hope. And that's really what this is all about. Keep hoping until someone says 'yes!' [And then keep hoping until a publisher says 'yes!']