I'm happy to see Flourish getting some notice, even though there doesn't seem to be a lot of love for it with the small mention. I'm happy Flourish user for well over a year now, and I feel as if Flourish's BETA tag is akin to Google's BETA tag. I honestly haven't run across a single issue with the library that would discourage me from using it in a production environment.
It's an unframework, it doesn't force MVC, but you know what? I don't need MVC for 90% of what I do. What I need to do is validate form input, accept a few file uploads, log that to a DB, kick off a few internal emails, and provide user feedback.
I think that some day I'll dig into Code Igniter, but as the only web developer/designer in the marketing department for a small company a tool that lets me stay agile and do less than conventional setups, as well as easily integrate into existing environments has been a godsend for me. It smooths out a lot of PHP's weird quirks, comes pre-baked with an amazing focus on security (oh thank god for your passion for security, @wbond), and in general just helps me get my job done.
Oh, and when people ask me what framework I use, I say "Flourish, it's like jQuery for PHP".
/fanboy
edit: One downside to Flourish is that I'm almost useless without it. What do I use to sanitize a POST variable again? How do I unescape before output? I've gotten so used to the Flourish classes I spend more time on Google than coding when I don't have access to it.