There is one of these at the knuckle up that's taking my money. It was my favorite bag in the whole gym. I don't know how much the glideboxx helps, i mostly liked it because it was the only bag with appropriate spacing from walls or other bags. I'm sure the moving action also made it enjoyable because learning to pursue and track something is part of training.
Actually, my favorite gimmicky bag holder was a horse walking machine with heavy bags on the arms so you could actually practice forward footwork without crowding up on the bag because it's constantly moving away from you....or toward you if you want to practice maintaining distance. That thing was awesome...
Only in a boxing gym do you find creativity like that