You should be good if you're targeting tablet. Phones however have a much narrower screen, and to support them reasonably well, Form Runner would need to support responsive design, for which we have an RFE:
https://github.com/orbeon/orbeon-forms/issues/1181This isn't as much of a problem on tablets, but of course, only testing your own forms will tell. And if in the process you notice any problem with Orbeon Forms on tablets, please just let us know.
Alex
--
Follow Orbeon on Twitter: @orbeon
Follow me on Twitter: @avernet