I have started to suffer with RSI and possible Carpal Tunnel and researched a number of different options on Mice to use to try to ease the strain on my wrist. I settled for the Vertical Mouse option and read a number of reviews about this Fellowes Penguin product.
I find it a really good grip and movement is very good with adjustable DPI speeds too. The wireless connectivity and battery life per charge are also excellent .
What takes a little time to adopt and adapt is the right click set up but after a couple of weeks I developed a good strategy with it ...more especially as I am left handed!
I am personally very pleased with the tactile nature of the units controls..