Yes, Tyler is Voq (and many including myself had thought); but to expose it now was great. And again, holy ship, Tyler snapping the neck of Dr. Culber made perfect sense for the situation, and was really surprising and shocking, but it worked really well. This is probably one of the best episodes they've done for the series to date - and I was pleasantly surprised by that.
Oh, and I LOVED the Turbolift fight sequence between Burnham and her former tactical officer - and her reaction in the Turbo-lift after - probably brought on because she had to kill him, and this was the second time she saw him die.