For the past several months, my 9.7" iPad Pro has functioned as my laptop and my 15" MacBook Pro as my desktop. Right from the start, I was blown away at how easy it is to type on 9.7" Smart Keyboard. Most of the posts on this site since the beginning of May have been typed this way.
On June 2, just before WWDC, I sent this to a friend with whom I discuss tech stuff every day:
Today, I'm really happy with the 9.7. Little table full of papers, big coffee, and plenty of room for the 9.7 w/keyboard. Can sit back and easily navigate with one hand. Ideal portable computer. I think I want the bigger one only when I want to sit down and do nothing but write. This is at least once a day. I'm not even sure, however, if the 12.9 would be better for this purpose because I have absolutely zero difficulty with this small keyboard. I would just like more space, more screen real estate.
I'm hoping the 10.5" will be a perfect balance of portability and productivity, but we'll see. I just opened Tap Typing to do a speed test, and this was the result of my typing test on the 9.7":
I'm looking to make a move to the 10.5, but I wanted to post a note about what a pleasure my 9.7" has been. The keyboard and pencil capabilities changed the game for me. On June 4, Forbes posted a "very long-term review" of the 9.7" iPad Pro and called it the world's best tablet. I would link to that article, but Forbes is one of those sites that has automatic popups and makes you click three times to get all the distracting nonsense out of your face and actually see what it is you are trying to read.
If you are considering an iPad purchase, you can check out my 9.7" here.