Fwiw when i bought my touchscreeen monitor i went from 2 - 23" side by side widescreen monitors to 2 - 27" (lower one on the desk - (touchscreen) tilted back 15-20 degrees, upper one on shelf, non- touch.
One caveat is that the view angle of the touchscreen monitor doesn't lend itself to too shallow/flat an angle. So you either have to tip it up more, or set your chair up higher than would be considered comfortable for a mixing desk/control surface.
Also, fwiw, i got more usefulness out of my iPad using AC7 but found the wifi connection to be problematic. I would still like to pick up a camera kit/midi port for the ipad to try setting it up with a hard midi connection rather than rtp via wifi.
i think the best way for sonar to move forward with touch would be to come up with a touch daw/ac-7 style "control surface" window specifically designed for touch, within sonar itself, rather than trying to customize everything to make touch workable (at least for me, my opinion only)