Great, great episode. My jaw dropped to the ground when we actually saw The First Doctor (colorized!) and Susan run off with the TARDIS at the beginning of the episode. While I found the splicing of Clara into old footage jarring the first time around, I quite liked the sequence when we saw it again at the end because it depicts her in the footage quality of that time period (although colorized for The First Doctor).
Richard E. Grant was great in his reprisal of the Great Intelligence, and while it's a shame we didn't get the Yeti, I thought the Whisper Men were effectively creepy and I liked the explanation of why they were dressed up as Victorian gentlemen in wintertime (as oppose to just "because it looks cool").
I also loved the clever workaround on hearing The Doctor's name (really, anyone who actually thought we would learn his name were fooling themselves) and it's interesting to note that Clara now knows his name (even if hear memory of reading it in The History of the Time War
Lastly, I loved the closure we got to River Song's character. While I'm sure we haven't seen the last of Alex Kingston, this provided some wonderful book ending to "Forest of the Dead" and further development of The Doctor/River Song relationship.
Even though I guessed it was coming, I grinned like a bloody fool at the sight of John Hurt as The Doctor. Of course, everyone is going to argue for the next six months which Doctor John Hurt is. Is he a pre-Hartnell a la The Brain of Morbius
Doctor? Is he The Ninth Doctor that ended the Time War and regenerated into Christopher Eccleston? Is he The Valeyard? Is he someone other past/future/amalgamation incarnation? It's going to be a long six months.
I'm looking forward to the 50th anniversary more than I was before but I'm still looking forward to Big Finish's The Light at the End