The great Heisneberg has made a mistake: Killing Mike!
It was the best episode of this season. So intense and solid and at the same time, pivotal . Walt has turned into a formidable and confident figure that is fun and at the same time hard to watch. Things will get complicated for him from here now on, though.
Killing Mike was not a planned decision. It was spontaneous and pointless. Walt even apologized to him, showing he was regretting his decision. Let's not forget that Mike had already tried several times to kill Walter, so in a way, he got what he deserved. This will obviously infuriate Jesse and horrify Saul though. They will hear about Mike's death, and since Walt was the last person who met him, it won't be too hard to find out about the killer's identity. This can easily end up in a big feud between Walt and Jesse.
About Skylar, I think there has been too much time spent to show Skylar's despair and frustration to leave it without a conclusion. I think it's all a build up for Skylar to finally decide to give Walt away to Hank.