I have always developed web software using a framework (Agile Toolkit) and it was helpful to me in all situations, but one question always concerned me:
In which circumstances it's NOT advisable to use a framework?
So a question to other veteran framework developers - when would you code in a raw good PHP
instead of your framework of choice?
There are many reasons that people will suggest not to use a framework.
There is also a very good article here that goes into other details. The author of this article starts out by talking about how he always was such a big proponent of frameworks.
I am always going to push towards making my own frameworks unless I start doing some freelance work. I am constantly updating my framework and learning more and more. You will never hear anybody say definitely use or definitely do not use a framework because it all depends on the use.
Edit: There is also a question over at the Programmers site on this: https://softwareengineering.stackexchange.com/questions/49488/when-not-to-use-a-framework
Edit #2: One last article about why frameworks are not necessary: http://www.amberweinberg.com/you-dont-need-a-framework-if-you-have-a-good-developer/