I was in a house about a month ago that has that, a place out in Sewickley. I had never seen it before up close. It is absolutely fantastic. The most even heat throughout the entire house. My only fear is if something would break it would cost a fortune to fix.
Baseboard electric would help, but it is really expensive as far as your electricity bill goes. If he has existing duct there and the furnace has some spare capacity, it would be far more efficient and just as comfortable to just add a duct (something he could do himself most likely)
They actually cause the house to lose heat if run in combination with a furnace. If they are your only choice its not too bad, but the venting of those systems can screw up newer style furnaces.