Had one installed on my 3130...used it for a few days, works great. It grabs the brush so well, I didn't need to use the grapple attachment in most cases.
It also works great for small tree removal; after a bit of experimentation with attack speed and bucket height, I was yanking 3-4" alders out of the ground in seconds. Just hit them about 2' up, raising the bucket as the tractor went forward. Teeth grabbed them perfectly, and ripped them out of the ground roots and all.
Attached is the only pic I have...you can barely see it. Tractor is two states away, or I'd snap up some better photos.