Launched on October 28, 2011, the S-NPP satellite carried an ozone mapping and profiler suite (OMPS) of sensors. OMPS opened its aperture door on January 26, 2012 to begin its Earth observation mission. After an early orbit checkout of the sensors for a couple of months and an intensive evaluation of the sensor data for several more months, an initial on-orbit calibration for OMPS was established using data acquired during these periods. To date in 2013, this sensor system calibration has been applied to produce OMPS nadir sensor data records (SDRs) and the resulting ozone environment data records (EDRs). This paper provides an evaluation of the combined performance of the orbital OMPS nadir sensors coupled with the ground data processing system for the current SDR's provisional status, and offers lessons learned during the first 1.5 years of operation. Examples of the sensors' short-term and limited long-term responses are provided, including cross-comparisons of OMPS EDRs with concurrent solar backscatter ultraviolet instrument (SBUV2) data from other NOAA orbital sensors, to illustrate the on-orbit stability of the data products despite some secular changes to the calibration and sensor.