I can see why Tony loathed her; Janice was a female version of him -- ruthless, conniving, prone to rage.
This scene is great too -- Janice calls out Tony and Carmela for Meadow's non-punishment, and Tony chucks his bowl of cereal across the room. Also love how Tony goes from intently reading the back of the Honey Comb box to making Hindu references.
Not only that, but they're both ridiculously hypocritical. totally agree that Janice and Tony are similar on many levels. There only real difference is that Tony has a dedication to his life and his family, Janice has more a devil may care attitude, but ultimately, they were both selfishly destructive in their own ways.
I had a friend once describe Janice as an underachieving Tony.