This version of Sherlock seems to have gone downhill, fast.
In the first episode you could hardly tell that it lasted 90 minutes, the writing was fast paced and exciting so the time flew by. This was not the case for the second episode.
In this instalment the story started off rather bland and the pacing really dragged. It's a huge shame as well, because they could have done something really exciting with this episode.
The first episode opened questions about Moriaty and Sherlock's brother Mycroft, but it was hardly touched on in this episode. Only in the last 5 minutes did we get a teaser that one of them is involved.
Considering that this is the only a three-part show there could have been more on that. And that would have been way more exciting. We can assume this will be touched on in the final episode, but why should we assume? We could speculate more, and be excited more, if we had been teased this whole episode about what's to come. This episode would have been fine if it was part of a longer series, but it's not.
Saying that though I've given the episode a 7.5 because it's still a lot better than most other stuff on TV at the moment.