Olympus has created a brand new mirrorless camera model - the Mini - to further segment the mirrorless camera market. At first look, the E-PM1 looks identical to the E-PL3. But on further inspection, one would find that the E-PM1 has far less buttons, knobs and dials.
Chester Tan

And that's where the differences end. At the heart, the E-PM1 offers the same hardware, same list of features, and slightly smaller overall dimensions.
  • 215 grams (body), 401 grams with 14-42mm kit lens, battery and flash
  • 12.3 megapixel High-speed LiveMOS Sensor
  • Full-HD 1080p movie recording AVCHD
  • Stereo microphones
  • Built-in image stabilization
  • Fast auto-focus system
  • 5 fps shooting

Simple and Minimal
 
The camera body offers a metallic feel, in contrast to the E-PL3 which has a acrylic gloss coating. The camera does appear somewhat bare, with lots of empty spaces, an unusual sight for a large camera, where many manufacturers would attempt to maximise the surface area. While in my earlier review on the E-PL3 I mentioned I don't really like the layout, I seem to like the E-PM1 more, despite lesser buttons and dials for me to do direct setting changes. This is because I have less buttons to be confused.
Chester Tan
Olympus attempts to make the best of the limited buttons on the E-PM1 to achieve ease of use. For instance, pressing the menu button will bring up the list of modes that would have appeared on the mode dial of the E-PL1. To go to the camera setup menu, you will navigate to the right-most selection. When reviewing photos during playback, you have to turn the wheel to scroll the images, while pressing the directional buttons zooms in and out of the image. To move around the zoomed-in image, you first press the "Info" button before you can use the same directional buttons. It does take some getting used to, but if this is your one and only camera, I believe you will get the hang of it over time.