Finished it today. While I definitely enjoyed it, I can just as easily imagine people hating it. I liked that it showed the raw emotions and complexity of the people involved. It felt way more like a meandering character study than a murder mystery to me. It was definitely moving, but I'm pretty sure that that mileage may vary.
Some things I didn't like were the parts he (Brian, not John) chose to talk or not talk at length about - I, for one, would have loved more on the clock maker friends and their relations to him, or even about the clocks themselves. I thought it lacked structure, if it weren't for the twist I would have stopped after the second episode. And I could not unhear the narrators tendency to talk like he could cry at every second? Each sentence he ended a bit shrill and higher pitched. It was a bit annoying.