I have to disagree about the vertical rotation - my grinder has the handle on top, spins horizontally and I find that I effectively use both hands when I'm grinding - right hand turns the handle and the left hand moves sympathetically. Hard to explain, but if you look from on top you'd see the hands crossing and uncrossing as I grind the beans.
With the handle affixed a la Handground, the non-handle-turning-hand (technical term there) can only serve to resist the motion instead of assisting with it.
I'm still practising with my Hario skerton, but I found yesterday that lifting it up off the worktop and using both hands is way easier than trying to hold it still and using only one hand.
My sister had one of those. I tried it out but couldn't get on with it; too fat to easily grip with my wee hand and the action was rough with a too short handle, sharp edges and plastic parts that didn't look like they'd last.
I have to disagree about the vertical rotation - my grinder has the handle on top, spins horizontally and I find that I effectively use both hands when I'm grinding - right hand turns the handle and the left hand moves sympathetically. Hard to explain, but if you look from on top you'd see the hands crossing and uncrossing as I grind the beans.
With the handle affixed a la Handground, the non-handle-turning-hand (technical term there) can only serve to resist the motion instead of assisting with it.