I didn't have the patience to read all the posts, so I apologize if I am repeating what has already been said. A marriage in crisis is never something to take lightly. While I agree that Kate can be a B, no one deserves to be cheated on. Jon is obviously not getting his needs met, but he needs to man up and communicate what those needs are. Kate needs to stop feeling sorry for herself, and admit her part in the deterioration of the marriage. They need some serious marriage counseling.
With all that said, I am sad because it is a show that DD11 and I like to watch together, and it's hard to watch right now. For their childrens' sake, I hope they can rediscover the love they once had for each other.