Have one... Only 5000btu though and in a metal building that has no insulation it doesnt do much so i took it out the window and use fans and create a cross draw that works better than the window unit did and helps a little with dust as well.... The building is only 200 square feet but even with that window unit left on for hours the window unit barely made any difference.
My father put a 14000btu unit in his metal shed thats only 10X14 and it still had trouble keeping it cool. He had to add some foam "insulation" (1" Styrofoam he shoved in between the rafters and studs) to make a difference.
His building is in direct sunlight and mine does have shade around it which gives me an advantage, but the cost of a better cooling unit and insulation is more than i want to pay when im honestly not in it that often... There is NO fish in there for me to catch
One day i might insulate it and get another unit to cool it off.... But ill have to be doing a bunch of work in there to make it worth the cost.