In almost ten years of all kinds of use around our place, the only application we have found where the turning brakes have been useful is for making square turns when mowing with the bush hog. For that, we set the cruise control, with the FEL off and in 2wd, of course, and the tractor operates exactly like a gear tractor.
Different users in different situations might reach a different conclusion, but for us the combination of HST, power steering and tight turning radius makes handling so easy the turning brakes are close to being unnecessary.