Totally did not see that coming. Going into the finale I had the typical Sherlock fan way of thinking. Moriarty reveal, which male actor they got, Napoleon of crime, etc. Then WHAM! That twist. Probably the twists of twists. But really, Watson as a female, the setting in NY...it was obvious this was going to be different in some capacity.
At first I was in "meh" mode. But thinking about it as the finale went on I ended being ok with it. Making M a woman and using the name Irene Idler as a cover is something literally no one ever thought of. And that's what made it great in a way. Plus it makes the relationship between Sherlock and M much more personal as Sherlock was so emotionally invested in "Irene".
Enjoyed it, can't wait for season two.