[eluser]Chris Newton[/eluser]
Some of the other frameworks are more feature rich (in some respects) but not too many can hold a candle to CI's documentation. I personally use CI because it's simple, cleans up my code, simplifies a lot of the irritating things about PHP that I don't like (pagination, forms, data access) and doesn't require a command line utility. UGH. The last thing I want to do is go to the command line time after time to set up my framework.
CI doesn't do everything for you, but enough to really, really help when you're generating applications. The difference between before and after? Before; programs that worked, but were hopelessly procedural with little reusable code, crummy validation, and lots of hidden bugs. After; programs that have components that can be reused and the peace of mind knowing that from a form data validation standpoint, my bases are really covered. Apps take me less time, less hassle, and they're a lot better. I can work on them being *cool* instead of just functional.