I used the EPL-1 mostly at ISO200, which is the base ISO. Found on the EP2 that ISO200 did better than ISO100, and the two have the same sensor. I ended up giving the EPL1 to my Nephew, getting an EPL2. The controls/firmware in the EPL2 are no where near as good as the EPL1, but the sensor is improved with regard to noise.
The M9, and M8, at Base ISO produce cleaner files than the EPL1 and EPL2.