I've recently become a fan of QCodo. Previously I had done a site in Ruby/Rails, then Cake, and I had heavily considered Code Igniter.
Rails is great, but at the time I was using it, finding a hosting company was a pain in the ass. Also, you may not feel like learning Ruby.
Cake was very good, but had a hell of a learning curve. In many cases, it seems like it tries to do everything, and makes things overly complex in the process.
Code Igniter looks to be the easiest one to pick up and hit the ground running.
QCodo relies on code generation for its data persistence layer, which I've decided I like more than the runtime reflection of the Active Record model that Cake and Code Igniter use. Also, since the code is pre-generated, the performance should be much better. More than anything, though, I like the event-driven architecture (very similar to ASP.net). If you have used and like ASP.net, you'll like QCodo. It is wonderful for building ajax, command center type applications in php. However, if you're looking to build sites for the spiders, you may want to look away because you don't have things like routes/customizedUrls (a common feature in rails/cake), and in many cases you don't have control over the exact structure of your HTML. As I said, it's like ASP.net on PHP.