First of all, the most notable improvement would be upgrading its sensor to hit a higher resolution – 3600 DPI. This will let you accomplish high-speed turns without the need for wide hand sweeps or even losing fidelity by increasing the cursor speed in the Windows control panel. All DPI levels can be adjusted on the fly (to 400, 800, 1800, and 3600 DPI) without having to install additional software. The report rate has also been increased from 125 to 1000 reports per second.
Apart from that, the optional button programming software has also been improved upon, where the mouse will be able to offer gamers the extra edge via its button and tracking configuration capabilities. With Logitech Gaming Software v8.0, it will throw in profiles for 210 games. Expect the Logitech Optical Gaming Mouse G400 to retail for $49.99 when it arrives Stateside this June 19th onwards. [Press Release]