>You're probably right. Learning a framework requires quite some time. But from my experience it's worth the effort, because once you get the hang of it, you're way faster than building everything from scratch.
Ok, I'll share my experience on these theme with you...
I'm a programmer with more than 10 year experience. I lived happily without frameworks until I bumped into Java. It was about 5 years ago. For our new project I decided to use powerful [url=http://www.springsource.org/]SpringFramework[/url] that is something like Saphire but without CMS. However that wasn't enough and I decided to use Hibernate as well - this is a powerful ORM class mapper to work with database. I think that it doesn't worth to say that the project was fully object oriented, polished MVC, and of course, it was absolutely independent of the database. But me and my colleague worked on the project for about a year and to its finish this project became absolutely not needed by our marketing team. Because time has been lost. A competing team of programmers working on PHP and MySQL made similar by the number of functionality project without any frameworks in 4 months... 3 times faster! Moreover the performance tests shows that their project performs requests several times faster also, because they make direct SQL queries to the DB and do not have many layers. I do not know why our management didn't fire us. If I would on their place I did this.
From that time I left me previous company, started my own one and wrote several projects in PHP without any frameworks which were full of functionality and was written enough fast - less than 2 or 3 weeks. Some of them were just for private using in the company, and a couple of the web-sites of medium complexity. I haven't experienced any problems with extending the functionality of these projects but there isn't such complex things like user management, authentication and authorization.
Than I hired a PHP developer to support our company main web-site and backoffice. Everything was OK, he did his job more or less well. Until we decided to install Drupal as the blog and CMS that we were planning to migrate our old plain PHP site to. He installed, customized and bug-fixed Drupal and required for us modules for 1.5 months. Can you believe that installation of the blog may require 1.5 month? Ok it's all in a lifetime. After he installed the blog I've charged him to develop a community based project using Drupal. Will you be surprised if I say that this project was never released? Yes, it was developing so slowly that I had to fire this programmer. When I tried to continue his work and develop with Drupal I (experienced PHP programmer) encountered with so many new conceptions, terms and layers that my brain became to a state close to insanity :) So I decided to discard the previous code and rewrote it from the scratch.
Why I'm writing all this bad for frameworks words to a community of the framework which (probably) successfully use this framework? Before I stumbled upon SilverStripe I examined several frameworks and CMSs and either they was too restrictive or they had too steep learning curve. SilverStripe at first seems like a very lightweight and easily customizable and much more important that it doesn't force you to learn custom form or DB entities creation language like Drupal. All you need to know is a plain PHP and some concepts from this framework. Unfortunately now I see that it's not so easy like I think before as I'm struggling with creation of the custom forms for the whole day. SilverStripe is my last point on using frameworks, either I'll use it or I'll never deal with frameworks at all and will write my own.
BTW here's an interesting article from PHP creator: [url=http://toys.lerdorf.com/archives/38-The-no-framework-PHP-MVC-framework.html]The no framework PHP MVC framework[/url]
Sorry for so long post.
Everything above is just my personal opinion, I suppose that I might be wrong or not enough professional. So consider it as a funny story from the life of a programmer, I do not want to offend programmers who uses frameworks or write them.