I've only just finished watching it a minute or two ago. I still haven't really processed everything, but I can say for sure that I enjoyed it. I enjoyed it a lot.
And people thought Steve Thompson wasn't a very good writer. IMO, he's more than made up for his not so good TBB. My word, this episode. I feel like this might be the beginning of Sherlock becoming a good man, as well as a great man. One of my favorite bits was when the supposed key code turned out to be fake. I was thinking that it was a ridiculous plot device, that it was unrealistic. And then it turned out to be not-real. I was right, but I didn't really suspect because I'm so used to tv shows using ridiculous things like that seriously.
Oh, man. Brain overload. I'm pretty sure the acting was brilliant though, all the way through. Must go watch again now. OH! Also, I officially love Molly. Yes. Now off to rewatch.