We've been using it with Cachet (https://github.com/cachethq/cachet) for a couple of weeks. Mainly it was to make testing our API easier, the new PHPUnit extensions are so freaking amazing - it makes unit testing a dream.
Other than that, other cool features I like are the LTS, dropping of the mcrypt extension requirement and also the broadcasting feature (which is worth checking out btw)
Also this release contains some code that I've committed too, which is always a nice feeling :)