I have the DK65 with a 15' batwing made by Taylorway. Like one of the guys said above, it will pull down in thick grass, but you just downshift. I generally go in high range, gears 1-4 depending on the height and thickness of the growth, on level ground. I have not noticed the tractor indicating any heating problems, although one time when i stopped, there was a twig smoldering next to the exhaust stack. After pulling it out and burning my finger, I figured there had been a good deal of heat put out by the motor, but the cooling system was keeping up fine.
Oh yeah, of course the AC was one and it was a very hot day. For my money, I decided to downshift in the thick stuff rather than pay a fortune for a tractor that could loaf through it, but be too much for everything else.
I was concerned with the pto switch/solenoid being too sudden (being used to manual clutches that you can slowly play out, like an old John Deere), but it seems to work just fine if you engage/disengage in idle.