There are a lot of pros and cons to every possible approach, so it was certainly difficult to choose a framework (or no framework) for this site. PHP and MySQL were natural choices as those are the technologies we use in our day-to-day work.
I seriously considered using Django (Python) instead of PHP because speed and scalability were important factors we needed to consider, and benchmarks seem to indicate that Python can be several times faster than PHP. We installed Django and followed some of the tutorials - it seems very cool, especially the auto-generated admin area. Not having any experience with Python though, I decided it was probably not a good idea to throw a new language into the mix as well. :-)
In the end it came down to starting from scratch, or using one of the many frameworks for PHP. We finally settled on Qcodo as it is fully PHP5 OOP, has nice form handling features and less bloat that some other popular frameworks. Running Qcodo's code generation function automatically creates your ORM layer by analyzing your database structure. Personally, I think this is a better approach than the run-time method employed by some other ORM solutions. Of course, it takes care of the CRUD for you, but it also generates a nice set of methods for working with any association tables defined in your model. Of course, you can still use manual SQL where necessary.
Take a look at the demos at www.qcodo.com

good topic, eric!
with all the buzz about rails etc deafening developers for the past few years i wonder are there people not using a framework? (me).
as someone who is developing a site in purely procedural php, i came to the conclusion a long time ago that a framework is the best way to do it. otherwise one ends up with a mess of code that rapidly is impossible to maintain. i have not used a framework yet, but i'll have a look at qcodo. taking a broad look at the issue it seems to be a more natural way to develop - a framework naturally assumes you are developing the app in an oop fashion (does it necessarily?) so we can write code such as user.displayProfile and have the framwork spit out some html with the users profile (more or less). of interest to me is the fact that all frameworks are using a relational database. why? they are freely available, well understood and easy to use. however, the "Object-relational impedance mismatch" (gasp(see wiki for more info)) seems to be an obvious objection to using a rdbms. if we are developing in oop why not use a oop database? well, there are not many that are freely available. some are, but are java only (db4o).
i would like to hear more about your experience with qcodo and the db you are using. how well did qcodo fit with your db schema? did you have to write some sql queries or did q handle everything? how did you decide to use qcodo?