Photo-based Bird Guides

Expert birder and ex-Austinite Rob Fergus has a very interesting new blog post: "Evolution of the Bird Photo Field Guide". Bird field guides are usually based on either photographs or illustrations (plates) of birds. I and most other birders I know are fans of the illustration-based guides for the reasons Rob describes in his post. So I've never paid much attention to the photo-based guides. But maybe I should! I'm especially intrigued by the Kaufman guide based on photos that have been doctored to be more useful for identification. My current bird field guide recommendations are here. Maybe I should reevaluate them!