I do - and it's awesome!
I use my 9.7" Pro extensively at work. It's also my portable sketchbook (I carry it with me everywhere). It's also my control device for my Drone.
I use my 12.9" Pro at home (art projects, and surfing/videos), though I'll take it with me if I'm going spicifically to draw.
On some occasions (though rare) I use the two of them together (taking notes while reading).
I have a pretty good balance with my Pros.