One concern I do have with such a widespread requirement for AFCI is building up so much heat in the panel, due to packing so many continuously operating (heat emitting) devices in a confined space. Are we going to be seeing 84 slot panel used for 42 circuits?
And what is the long term reliability of AFCI? We haven't seen them in long term (and in all that heat), yet.
I think I would rather see AFCI outlet devices, since at least for residences, cords for utilization equipment may be the greatest risk (not that a nail driven into an NM isn't a risk).
