I use CC most of the time while towing. Once I get out of traffic, a combination of CC and exhaust brake make hills uneventful. I set the speed and stay within 2 mph regardless of hills. This allows me to keep the speed within the posted limit. I like to drive fast, and towing between 55 and 60 is SLOW!!!!!!!! But 55 is what it is here in CA. Not worth the speeding ticket.
I also get a kick out of setting my speed and having people fly by me at 70+ on the flat land, only to have me pass them up in the hills as their 3/4 ton, raised truck, pulling a 40+ foot, loaded, three axle toy hauler is struggling to get 35mph up a 6% grade! Yes, we see this all the time here in California. Too many people listen to the salesman that said their truck can pull it. ;-)