To be fair, most air conditioned horse trailers have some form of bling towing them around. Also, most people I know that own 3/4+ ton pickups never hook up a trailer.
I say if you can afford it, by all means, support the economy with your tax dollars on that $70k+ pickup. Where I live, a/c on a horse trailer doesn't seem odd. It would have struck me as odd when I lived on the Kitsap peninsula in Washington though.
This is the perfect vehicle for someone who has the cash (obviously), tows what the majority of people would tow (3000-10,000lbs), doesn't tow more than a day or so a week, and wants that fuel economy. Many purchases will be people buying it because diesel has become kind of a status symbol with trucks, though most people would be better off with gas.
I would consider a low mileage, used one as a daily pickup with a 1 ton parked for heavy work. I don't want anything more than an XLT though because I like the cloth seats and lack of Sync and other doodads. That means this idea is out for me since they'll only offer it in the Lariat and up. I'll keep my half ton with the 5.0 for daily work and continue looking for a 1 ton for the heavy lifting. The 1 ton will probably be gas as well though, since it wouldn't see frequent usage.