See discussion at http://drupal.org/node/1911178#comment-7140322 and onwards.
sun's comments on there reminded me how much I dislike the fact we're using Symfony bundles in core.
There's several methods on the bundle class that we completely exclude from calling after- those methods don't really make any sense over events or hooks, and since we don't require modules to have a bundle class, we were doing nasty file system checks to see if the bundle exists each time before calling those methods.
This means that bundles are only used for service registration, and no-one has yet claimed to enjoy that over just implementing a hook.
Symfony itself allows for defining services via YAML, which is what we're also using for routes and now .info files, so if we moved to that, could we not drop bundles altogether?
See http://symfony.com/doc/2.1/cookbook/service_container/event_listener.html for an example, there's a PHP/YAML/XML tab showing the differences for an example event listener.
PASSED: [[SimpleTest]]: [MySQL] 54,158 pass(es). View
PASSED: [[SimpleTest]]: [MySQL] 54,071 pass(es). View