Parenthetical.net has a few reviews of Cybils nominees:
Benny and Penny in Just Pretend by Geoffrey Hayes
Babymouse Monster Mash by Jennifer L. Holm and Matthew Holm
Nightmare on Zombie Island by Paul D. Storrie
The New York Times reviewed Cybils nominee Skim by Mariko Tamaki with illustrations by Jillian Tamaki
Then J.L. Bell at Oz and Ends talks about how graphic novels are treated in Great Divides in the Comics World. Included in the post is a link to a Christian Science Monitor article, Graphic novels, all grown up, which includes a definition for graphic novels: "...extended-length illustrated books with mature literary themes..."
Of course, mature means different things when you're talking YA versus adult graphic novels and something else entirely when you're talking graphic novels for kids. But for those of us who are educating ourselves on the subject, it's a start.