The Time Demons were downright creepy. Reminded me a bit of the Catalyst from last season. But a very inventive episode. Kerry, Clark, and Farouk's Power Point presentation adventure was pretty much like reading a comic book, down to their comments appearing like speech or thought bubbles.
Also, it wasn't until some folks on Twitter pointed it out that I learned that the quick scene with Michael Chiklis was from The Shield. As someone who has never seen that series, I was thrown for a bit, but it did work as an example of how David meddling with time, as well as the Time Demons themselves, were messing with the fabric of time and space.