I received my Children's Writer's & Illustrator's Market 2008 last week and found it to be a good time saver, but a little padded. The markets are not as plentiful as I would have liked, but that may be because I'm use to the enormous Writer's Market. There are simply fewer markets that cater to children, so the smaller number of markets is to be expected. However, the size of the book can give you a false impression of the number of markets it contains. The market sections are broken up, very frequently, by filler content that is so specialized that I found it useless.
Aside from the filler items, the book itself is a huge time saver for anyone looking to get into the children's market. It has extensive listings for agents as well, negating the need for two separate books. And, if you're an illustrator, there are book and magazine markets, and agents, for illustrators as well. The listings seem more or less evenly divided between those for authors and illustrators.
In all, I like the book and it's saved me hours and hours of searching through Writer's Market for listings that will accept children's fiction, and the agent information is invaluable. But, I would have liked it a bit better if some of the filler had been cut out.