I have to admit, the Surface Book with its detachable hi res large screen is certainly going to make people think hard about it when pitched against the iPad Pro, especially if they aren't already part of the Apple ecosystem.
I had been planning to buy the iPad Pro myself, along with a Pencil, and replace my Lenovo Yoga 13 sometime later, but I'm seriously going to have to reconsider now. It's not that I'd be abandoning Apple (I've made far too big an investment in my kit to do that) but that the Surface Book would cover a lot of bases that would have otherwise required me to buy two separate products.
Well played, Microsoft. Very well played.