Not sure how to feel towards my father?

My mother left my father five years ago after he had an affair with another woman. It was not the first time he had cheated. The first time was when I was just a baby. For about the last ten years of their marriage, my mother worked an opposite schedule than my father. The job paid well and she felt she needed to be prepared for a "rainy day" - perhaps the day that my father would cheat again. My father spent most of his free time alone at home doing things around the house and watching TV. He went through bouts of mild depression from boredom and loneliness. When he came clean about the last affair, I couldn't remember seeing him happier. He was convinced he and his mistress were going to be together and live happily ever after with her two small boys. But, in the end, she chose not to leave her husband. My father is now married to a woman 15 years his junior that he met through an international dating service. I don't know how I should feel towards my father. He has inflicted a lot of pain on my family over the years. But he claims to have never had a "soulful" connection with my mother although he said she was a good wife and mother. Was my father justified in looking outside the marriage for fulfillment, or should he have counted his blessings and remained faithful to my mother and tried to work out their differences? I am conflicted about this and am interested in other perspectives. Thanks.