Holy shit this was the best doctor who episode in YEARS. I got tingles as as soon as they realized they were on the edge of the universe.
How about the fact that this whole episode was just our two leads. They both really showed their acting chops.
What was a really good peice of narrative for our Doctor was the fact that his fast and clever brain was a detriment to stopping our monsters of that week.
Just superb writing and acting through and through.