On the Symfony blog, there's an article posted by Ryan Weaver helping to explain the new service configuration changes that are included with version 3.3 of the framework.
In less than 2 weeks, Symfony 3.3 will be released. It comes with a lot of new stuff, but there is one feature that stands out: the new service configuration. I am very excited about these changes: they're designed to accelerate development, make Symfony easier to learn and encourage best-practices (e.g. injecting specific dependencies instead of using $container->get())... without sacrificing predictability and stability.
The post includes an example of what the new configuration file format will look like and briefly explains some of the changes. For those interested in a more in-depth look, they also link to this page in the Symfony documentation that goes through the changes step by step. It covers the autowiring by default, autoload of services, controllers being registered as services and more. If you're planning on making the move up to v3.3 when it's released (or sometime after) definitely check out this guide to make the transition easier.