I would LOVE to destress over some coloring, however due to some nasty orthopedic issues I've had some bones in my hands removed, and my thumbs fused and I can't really hold a pencil well.
But if I already had an iPad Air 2, I'd hold off unless I really needed the drawing features enabled by Apple's excellent Pencil stylus (sold separately for $ 99, # 79 and AU$ 165).