the Logitech G3 (MX-518) uses the Avago 3080 optical sensor and the Logitech MX-518 Rev 2 uses the Avago 3080E optical sensor they both have the same performance but the Logitech MX-518 Rev 2 has a data saturation problem.
the graphs above show when Setpoint is installed there is going to be data saturation no matter what value the resolution is set to. to minimize this it is recommended not to install Setpoint, overclock the usb port and set the resolution to a lower value than 1800 CPI because at 1800 CPI it is way too erratic and the performance loss brings it down to a OS MLT 04 optical sensor (Microsoft Intellimouse Explorer 3.0).
Logitech MX-518 Rev 2 owners shouldn't have a problem with this information since the Setpoint drivers can be difficult to install and if you manage to get them installed they are next to useless.
please don't shoot the messenger!