Spoiler Alert
Sherlock was back today, (I will write some spoilers so if you haven't watched it and are planning to then stop reading) and I just think it was a bit muddled. I am glad Mary got killed off, in fact I don't think she should have ever been introduced, as she played a large part imo in making the third series so much worse. I think today they have tried to make it nore clever, more aligned with Series 1+2 but they seemed to include plot twists not for the benefit of the story but just to say 'Ooh, look, plot twist!'.
The story arc itself was fine, case turns into a more important one which implicates unexpected people and similar to some of the better episodes, but it just seemed, to me, to be missing a trick. It was too convoluted and not clever enough; too involved and personal but not gripping. They tried too hard. This was disappointingly evident in the unnecessary slow motion and 'edgy' shots, like the tea dropping and Cumberbatch's face morphed with the bust of Thatcher (I understand the symbolism in that, but it is still utterly superfluous). The blue water reflecting on his face earlier in the show (when he was talking to Mycroft) was foreboding and made sense with the ending, so I'll let it slide.
In short, better than Series 3, but still a few notches below 1 and 2. Hopefully without Mary it should improve back to how it was.