Believe it or not I had that and the logitech ones. The index/middle finger track ball is a bit less precise due to how our fingers are built and it's a pita to clean them for both the ball and the rolling axis and the housing(since it's a concave shape). Eventually I caved to the modern censor mouse since no cleaning is required. (well, except those pads adhesive attracting dust etc. )
Believe it or not I had that and the logitech ones. The index/middle finger track ball is a bit less precise due to how our fingers are built and it's a pita to clean them for both the ball and the rolling axis and the housing(since it's a concave shape). Eventually I caved to the modern censor mouse since no cleaning is required. (well, except those pads adhesive attracting dust etc. )