Con The default DPI buttons are placed in an uncomfortable position
By default the buttons place above and below the scroll wheel control the DPI. However, they are placed in an awkward position since they are too close to the actual scroll wheel and it's very easy to scroll accidentally when trying to press these buttons.
Con Fewer programmable buttons than competitors
Most gaming mice in this price category have at least 11 buttons. The Logitech G400s has only eight. In addition to the left and right buttons it has a clickable scroll wheel, two thumb buttons, one button above the scroll wheel and two below it.