I had a feeling this would happen. I think OWI and JAW know the value of Steam but maybe the experience with the MO and the SW port have a bad taste in their mouth. It could be as simple as Stew's love of Sony and the Playstation and to give the PS4 that bit more appeal over the XBone? Who knows. Personally. It's only a month and I can wait. I've wanted a reason to get a PS4 anyway.
It could be worse. You could be a Wii U user.
