I reviewed the Cintiq 21 with SketchUp for Canadian Architect magazine several years ago. I love the product for retouching photography, but…
this is not a tool you'd use with Archicad or any task that wasn't "sketchy."
It is fine painting with a metaphoric brush, but using your entire arm and stylus to operate dialog boxes or precisely place Archicad elements is tedious and tiring.
Swinging around in SketchUp is quite novel at the beginning but drudgery at the end.
We forget how wonderful the mouse is, with tiny gestures being powerful and plenty of resting between gestures. But doing those same tasks with a stylus for more than a few minutes is awful. To be a bigger success this tool needs fingertouch surfaces for quick touchpush of dialog buttons with one hand and drawing with the other.
Good luck.
Dwight Atkinson