Create a page without writing a line of code. Update content directly on context.
Use symfony cache, and APC if available.
Automatically combine and compress your CSS and JS.
Using Zend_Search_Lucene, Diem automatically indexes all the site's pages.
Just add a search widget on your site, write some CSS, and you're done.
Security is managed by symfony :
The SEO team works in a clean interface, directly on the page, or using automation patterns.
Manage files in admin. Drag&Drop them to your content in the front.
Project browser, code editors, and even an ajax Unix console ! Some interface designers don't use no more IDE...
This list is a work in progress