Loved the episode one of the best so far and looking forwards to next week. I think everyone else had made comments about most things that I loved, plot holes etc. So I'll not add to that.
The one thing I will add... with the Infocom reference someone made earlier, some of it seemed almost in homage to the Hitchhikers Guide to the Galaxy game in the way the looping time element worked. Not the same but very much in the feel of it. Not surprising seeings as how DNA worked on the show. I also recall one of the Doctors made a reference to knowing Arthur Dent,the 2005 episode The Christmas Invasion, which features the Doctor saving the world in his pajamas, the Doctor makes reference to himself being very Arthur Dent. He then mumbles that Dent was a nice man
Also it strikes me that some of the imagery used was much like Monument Valley, moving buildings, castles in the middle of the sea, lateral puzzle solving etc.
Wonderful stuff all round, think I'll watch it again tonight!!