I can't believe that the reviewers before me (except one) saw the same production I did. Honestly, as it was concluding, I was amazed I'd enjoyed it as much as the very best crime thrillers I've seen from Britain, Scandinavia, Belgium, and elsewhere. I found it exhilarating.
It may not have been flawless, but I thought everything was above average to exceptional. The main actors were phenomenal (two secondary parts were a few beats off but not terrible). The photography and editing were great. The story was compelling for nearly the entire four hours. The third episode slightly faltered for me. In the end, that may have been best: I'm not sure I blinked during most of the fourth episode.
Perhaps other reviewers had seen this specific story done (like Professor T, another great one, it seems to be a popular remake) before. They walked into it with expectations that weren't met (too similar or dissimilar)? Don't let them dissuade you. If it's caught your interest, give it at least 20 minutes. I can't help but think most will enjoy. I wish they'd have continued the story. Instead, I'll have to look for other works by the makers of this fine series.