-1 the memcache store removal.
Users that have RHEL for their servers will have some difficulty with getting the memcached php extension currently as I have not seen a new release software collection with it.
I am nearly done building a LAMP cluster that is using memcache and it works just fine. Memcache was not my first choice but using a third party repo to get php memcached installed was out of the question.
It would be make upgrading to moodle 2.9 VERY difficult to do if memcache is no longer supported (depending how memcache acts being a add on instead of part of core moodle code).
PS: How does this change impact memcache if it is a add on plugin when it comes to session handling?