I'll give the spinner a shot when I get my new tractor. The one I have now wouldn't work so well, both because of the awkward angle of the wheel, and the lack of pwr steering. Although with the mower raised, it only has about 200lbs on the front wheel anyways, so it steers pretty easily, but doesn't necessarily turn...
I did a few hours of brush work the other day, just backing in. The only problem I had was I bent the lower edge of the shroud into the blade by backing into trees that were too big. I beat it away from the blade, but I may add a piece of angle to give it some strength in that direction. While I'm at it, I may also cut some teeth so that it would cut down some of the small stuff as I'm backing in.
The main thing I really need is a live PTO... That will make all the difference in the world for this type of work.