Alex Cooke at Fstoppers has written a review of the iPad Pro 12.9 as a mobile photography workflow solution. Here is an excerpt:
”As mentioned before, Lightroom Mobile is actually my preferred place to cull. It renders previews instantaneously, and the tactile flow is just so much quicker in my opinion. Plus, I like to curl up in a chair when I'm sorting photos, and the iPad Pro is perfectly suited to this. A lot of my shots are from events or the like and don't need work beyond adjustments in Lightroom. In this sense, I prefer this workflow to a desktop. It's tremendously quick, and I prefer the touch interface to a keyboard and mouse; I've found the muscle memory I gained from it enables quicker edits, plus the ability to draw directly on the photo and watch changes in realtime is an irreplaceable experience.”
The review is very thorough and I recommend a read.