I have an E-PM1 and it is a little gem though it does not seem to get mentioned a lot around these forums. I recently added the Oly 45mm to the kit and it really shows what the E-PM1 sensor can do. I'm sure it's not as good as the 16Mp ones, but it is pretty amazing.
The E-PM1 seems like a very well built camera and the photos I have seen from it are excellent with great colors and plenty of dynamic range. You should really enjoy this camera and not worry about any small differences between it and the newer 16mp sensors.