Based on the advert that the BBC first put out for it, I was pretty sure I was going to hate it. Having watched all three episodes however, I can safely say that that was probably the best thing to come out of the BBC all year! It felt extremely well written, and Cumberbatch and Freeman work great together. Some of their 'three's a crowd' scenes in the second episode were comedy gold.
The only downsides were some of the casting choices, and the peculiar way they communicated 'texting' and 'browsing' visually on screen. For the former, the actress playing the police woman comes to mind - the one that was in Waterloo Road. To be blunt, she just really didn't fit the role. For the latter, alarm bells started going off for me when the word 'Wrong' started bouncing around the screen PowerPoint-style in the first episode. I suppose it wasn't so bad later on when they'd toned it down, but still, it never really seemed to put across any information that we couldn't have just guessed for ourselves.
On the whole though, hugely enjoyable, hope they do some more in the future.