Possibly the most exciting piece is the performance wins for memcached_clone(). In a lot of situations developers use libmemcached with Apache. Each time an Apache process has to be created a clone() call is made (in some PHP architectures this happens with each request). On local testing this went from around ~300ms for me, down to ~28ms in one particular setup.
If you haven't checked out memslap in recent versions you should. Schooner Technology did quite a bit of work on the tool. You can read up on the new version here.
We also have updates to memcapable, so if you are interested in seeing how compliant your memcached appliance is, you should check it out.
You can find the latest and greatest here: