Saw the Sherp in action recently. On it's ideal terrain, it's quite impressive.
Simply put, it operates with the ground pressure of a medium length tracked vehicle with none of the caveats of tracks. It will navigate terrain that more conventional wheels and tires cannot. Swampy, marshy type areas are where it really shines, as well as delicate terrain.
Unfortunately, where i live i would have to echo many of Mark W's points above.