People who didn't like the last scene are capital H HATERSZZZZ!!!!!! You don't fuck with the Stormborn, the Queen of the Andals, the Mother of Dragons, and the UNBURNT! The Khals didn't know who they were fucking with threatening to gang-rape someone who was actually worlds more powerful than them and they got burned alive for their troubles.
The fact that Daenerys finds the practical way out of a situation looking at the larger consequences rather than trying to be Ned Stark type honorable is one of the best features of her character and why she's the greatest heroine in the history of fiction. Of course she'll burn the Khals alive to save the world with complete confidence that her plan will work as it was destined to.
Really thought the whole episode was pretty good. Not great, but a vast improvement on the rest of the season. A very strong 8/10, possibly even a weak 9/10.