The reviews have been overwhelmingly positive, including this from TV Guide's Matt Roush:
Five Days, an HBO-BBC collaboration airing over five Tuesdays, goes for the emotional jugular as it immerses us in the anguish of a family trapped in limbo after a young mother suddenly vanishes. As police suspicion and relentless media scrutiny take their toll, a blue-chip cast of British pros (David Oyelowo, Penelope Wilton, Patrick Malahide, Edward Woodward, Janet McTeer) elevate the melodrama. The suspenseful story jumps days or weeks between episodes, each hour focusing on a pivotal day in the investigation. I watched with an escalating sense of dread, but still was unprepared for the powerful twists along the way.
I found episode one riveting, and was reminded of the days of British mystery brilliance like Traffik, Cracker, and especially Prime Suspect. Writer and creator Gwenyth Hughes gives a good interview about her inspiration and her process HERE, nailing the importance of getting the ending right in these types of programs...
I think when you're doing anything that has any kind of whodunit element, the outcome of the whodunit is enormously important to the audience. But you've got to sort the whodunit part out and that's very difficult, especially over five hours. It's quite a lot of suspects to keep going. And you've got to reach a point in the end when you reveal whodunit, it's both enormously surprising and the only possible person who could have done it. But at the moment of the reveal, the audience goes oh, oh of course. It causes much lost sleep to get it right.
So far it's being played out as a closed mystery. And it's a hard enough to keep the audience guessing and the ending a surprise in a one hour episode, much less over five hours. I truly hope it's successful.
I know its a little pointless to single a show out after its already aired, but I believe you can still watch episode one at the HBO website. And hopefully Movie Central will repeat it again later in the week.