Exactly what we've been waiting for:
Spencer blows it out of the water with his comparison, I think he does keep it objective. All 3 devices have great Pros and some Cons, so it boils down to the specific scenario of the user.
In my case I currently don't own a Personal PC (desktop nor Laptop). I do have both of those for work, but I can't do large personal projects on those since they are company property. I been getting away with just owning an iPad mini and borrowing my wife's Macbook Air occasionally. So my dilemma continues:
I WANT the iPad Pro... but I NEED the SP4...