I'll admit my ZTR bobs and weaves enough that I've learned to treat it like swimming, don't get on that ride within 20 minutes of eating, or you'll get a cramp. It is quite a core muscle exercise.
But I work long hours sitting at a desk all day and night, so getting out and exercising those core muscles for 90 minutes every 4th day is just what the doctor ordered, for me.
I would guess that if I had the self-control to drive my ZTR as slow as my CUT can reasonably do across a lawn (i.e. 4 mph), it'd be a much smoother ride. But I'm a g-force junkie, and just can't help but punching those levers full-forward coming out of each turn. It satisfies my inner child.
I'm probably also being unfair to the CUT, saying it can't do much more than 4 mph. That is indeed the speed I've noticed it starting to buck pretty badly offroad, but that's as it's typically configured with loader and rear ballast. If I removed that equipment to mow, given it's all weight extended out past the wheelbase, then I'm sure it could go a bit faster.