Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Horrible ergonimic design

I bought this mouse thinking it would eliminate the finger pain I suffer in my left click finger. Although the trackball allows you to avoid using your left click finger it causes pain and stiffness in the rest of the fingers because of the poor ergonomic design. I find my self tensing most of my fingers to hold them off the right click button to avoid accidentally right clicking which happens quite often. This is because of its ambidextrous design. This was a waste of money. It may be good for a casual user of mice but not for someone who uses a mouse 8 hours a day as their profession. I've gone back to using my Evoluent mouse which isn't perfect either but causes me much less pain. Do not buy this mouse if your RSI problem is in your fingers. I am now looking for a foot pedal mouse instead.