Lately I've been hearing so much about how publishers and agents are looking for middle grade. The latest:
Agent Susan Hawk's wish list includes middle grade that goes beyond goofy boys and quirky girls.
Kat Salazar is a new agent, actively looking for middle grade. You can find more info about her in a recent agent spotlight at Literary Rambles.
Agent Mary Kole has updated her wish list (see sidebar of her blog) and writes about the need for "more meaty" middle grade" and notes the continued demand for fantasy and action-adventure in her report on Bologna.
So if you're writing middle grade and looking for representation, keep working and keep trying! There are opportunities out there.