Congrats on the full requests - that's a good sign!
Personally, I don't usually get a lot of good feedback with rejections. Of the 7 requests for a full I've had on my current book, only one provided me with useful feedback so far... and she was requesting revisions, not just rejecting and making suggestions.
I know you have some good energy going here, but I wouldn't query too many agents at once. (As in, not your entire list at once.) You may get feedback, but if you are anything like me you may find yourself revisiting and fine-tuning your query even after you are certain it is polished. I am a bit psychotic when it comes to query letters, though. They keep me up at night. Obviously, it is entirely up to you and what you are comfortable with. I try to not have more than 8-10 queries out at once so I can make revisions based on feedback or mailbox tumbleweed. That's just me, though.