Thanks for responding, everyone. Unfortunately I haven't really seen a response from anyone that has evaluated a framework and given it a thumbs up or thumbs down. If you've played with any frameworks, please let me know in this thread. Just give it a rating 1-10 and list any pros/cons.
FYI, I found a pretty complete list of PHP frameworks on good ol' DMOZ:
http://dmoz.org/Computers/Programming/Languages/PHP/Scripts/Frameworks/
I'm taking the time today to play with a few frameworks. The first I've tried is PHP-Cake. Unfortunately I'm really disappointed in it. I might come back to it later but it seems rather...half baked. Sorry, I couldn't resist. The website for the site is terrible. They have a wiki and a bunch of other archived support documentation, but there's huge chunks missing. I couldn't for the life of me figure out how to set up a "hello world" script.
It uses mod rewrite, but there doesn't seem to be any base rules set...I loaded up the default index.php and the browser just hung. I'll play with it a bit more but in general, the project is new and it feels new. Hopefully, they'll have someone to revise the site, add documentation, and make the initial installation much easier.
I'll keep posting to this thread as I evaluate more frameworks.