[celalo]

I should not say 'yml based settings' is a deal-breaker but it sure is a very good way of configuring the project. I personally take advantage of this convenience quite often. You can easily update your schema through yaml files and you can build&generate your whole model including auto-generated forms & filters for CRUD in a glimpse. I believe this is very friendly with agile principles.

[andypants]

But you can just as easily update settings stored in other formats.

[celalo]

Yes you are right. But It does not have to be all about yaml format itself. Instead, Symfony utilizes this format to get things done in a fast and neat way, in comparison to others.