New features seem to be the same as in the also-just-released 2.8 version.
Listed at http://symfony.com/blog/category/living-on-the-edge, they are: Redesigned Web Debug Toolbar, Redesigned Profiler, PropertyInfo component, Deprecated service definitions, Guard authentication component, Service Auto Wiring, LDAP component, Console improvements, Symfony as a Microframework, Form improvements
Listed at http://symfony.com/blog/category/living-on-the-edge, they are: Redesigned Web Debug Toolbar, Redesigned Profiler, PropertyInfo component, Deprecated service definitions, Guard authentication component, Service Auto Wiring, LDAP component, Console improvements, Symfony as a Microframework, Form improvements