The thought of hammering 6,000 typical 1-inch long ringshank underlayment nails to lay around 1200 s.f. of plywood sounds like an awful chore. I don't know of an air nailer that shoots that kind of ammo, but I do have a roofing nailer that shoots 1" roofing nails. That sounds a lot easier... or I could get an air nailer that shoots the 1/4" crown lightweight staples and stitch the plywood down on a 3"x3" grid, which is somewhere around 21,500 staples.
So... are there any other options? Using roofing nails sounds pretty good to me at this point... any opinions?