I thought that Laura Carmichael was ridiculously good in this show. Agatha was someone that I felt sorry for at times but also I really despised her as well. The other actors were somewhat average; I just don't think that their characters were as memorable as Agatha was.
The show overall was incredibly depressing with very few moments of light relief, and I always finished watching feeling pretty low. The first couple of episodes were pretty good; but the ending was quite unsatisfactory.