We just finished watching both sets of DVDs at 2 episodes per night.
Bit of a spoiler here:
Before last night's session I said to the missus "the first episode will end with Stella in Spector's hands and in the last one she'll be rescued". I was glad to be wrong. I also liked Rose Stagg being allowed to survive: we all expected her to be dead, which would have detracted from the final denouement.
This serial has been atypical all the way through: the usual stereotypes were avoided, there was none of the "I've got a gut feeling, Jim" crap that comes up repeatedly in US serials**, only a very slight suggestion of the usual "pressure from above" syndrome, and the procedurals, in particular with the dispatcher and the interviews, were brilliant.
It was also great to take a bath in my home-town accent.
We noticed the similarity to
The Killing, but I think I preferred this for the lack of peripheral issues. None of it was boring. But like the killing, I don't think it will be particulary rewatchable.
**I wonder if they started calling them mini-series to avoid confusion with Cheerios.