In my opinion, the Evoluent vertical mouse is probably what the standard “mouse” should look like, because it offers a high degree of ergonomic benefit and yet remains easy to use without special training. The Evoluent design simply takes an ordinary five-button scroll mouse and turns it on its side, untwisting the user’s wrist from its standard position into a natural “handshake” posture. At the same time, this enables the weight of the hand to rest on its sturdy side, instead of being painfully piled on the wrist. One reviewer, who had gone through many ergonomic mice, described the sensation of using the Evoluent this way: “Like when you’ve been standing on the bus for hours and somebody finally gets off so you can sit down.”
See our full review here. Here is a short commercial video from the manufacturer.