Just finished watching Time of the Doctor. I know how the Internet hates spoilers so I'm not going to bother providing spoilery details, just the bits that are already known to everyone:
First things first - it ties up all the loose ends that managed to crop up during Moffat's run, including ones that he accidentally brought up while addressing loose ends from previous showrunners. Off the top of my head, the issue with how many regenerations he's had so far (and yes, he's run out of regenerations by the time he turned into the 11th doctor, as for how he managed to regenerate one more time into Peter Capaldi's doctor - you'll just have to watch), who really blew up the TARDIS, what happened to the cracks, what the Silences really are, and how the doctor died on Trenzalore. There are others, but the resolutions happen so fast that you really need to just watch the special on your own while keeping an open eye.
The Time of the Doctor special actually plays out like your typical Christmas special at first, with the Doctor helping Clara cook Christmas Turkey and pretending to be her boyfriend while wearing hologram clothes that only Clara sees (so technically, clara brought home a naked doctor and presented him as her boyfriend to her parents and grandmum.)