Some stats of my own vbulletin 3.8 site (with Tapatalk) by OS:
Mobile browsing is a big deal for me. I actually wonder how many users in that 12% or so have a desktop as well? How many people go out to buy a smartphone these days to use facebook etc? No phone line/DSL/PC-headaches for our non-tech friends. And the better the mobile experience the more they will come back.
Nothing you don't know already, but certainly a consideration I have as when to move from vB (and not if

).
Keep up the good work.
Andy