This is a really important Header and Footer release since you will find a new interface, CodeMirror with syntax highlight, better mobile codes management. Hopefully without too many bugs even if it is a major release.
The most important new feature is the injection in the middle of the post, or better an engine that injects following you own rules. More on this topic will follow with a couple of articles.
Injection on bbPress forums, posts and replies should be more stable and easy to configure. There are even generic injections which search for some code in the generated page and replace them. More on that on next articles.