KW did a fantastic job on the rule of Midred Pierce - a hard working woman who put all her love on her daughter yet at the time spoils her daughter until it's too late. Her performing was so convincing that every moment of Mildred's appearance on screen was virtually real. I believe I saw one of the best acting on "mother" (another on I could recall was Night, Mother by Anne Bancroft).
I think it is precisely this theme (passion) that gave KW plenty of room to display her talent of acting.
After I finished watching the TV series, I found there is an original movie in 1945 by the same name. I too watched the movie. I must say, KW's performance is not any less than Joan Crawford's, except KW's reached a deeper level of exploring the complexity of a mother's emotion.
Prior to watching Mildred Pierce, I watched Revolutionary Road and The Reader. KW's was leading actress in both movies and I was highly impressed. I will be totally proud of being called a Kate Winslet fan. That's how much I love her.