With shockingly tall stature and non-traditional curves, vertical mice require some adjustment to use. But the purported payoff, if you're to believe mouse-makers, is greater arm, wrist, and hand comfort due to a more natural hand position.
The Lift puts your hand at a 57-degree angle with the desk and in a handshake-like position. There isn't hard evidence proving that a vertical mouse can alleviate issues like carpal tunnel syndrome or repetitive strain injury (RSI). Logitech is also careful not to make any strong promises beyond stating the mouse "takes pressure off the wrist while promoting a more natural forearm posture throughout the day."
The point is, your hand does have to rest on something. Right now, for my "horizontal" mouse, my wrist rests about 15 to 20 degrees, on a cushioned pad projecting up from the mouse pad. To move my current mouse, I just twist my wrist joint left or right without moving my arm. So whether one actually needs a vertical mouse, or just better wrist support with a current mouse, really remains to be seen.
See Logitech’s Lift is a vertical mouse that’s easier to grasp
A trimmer build and left-handed option make the Lift extra helpful.