This camera is simply amazing. Image quality and performance are definitely good enough for most professional work. I say 'most' because like all mirrorless cameras it uses 'Contrast Detection' Auto-focus, as opposed to 'Phase Detection' Auto-focus used by DSLR's. The up side is very fast and accurate focus, the down side is less than stellar 'Continuous' Auto-focus when tracking fast moving subjects.
Because it uses an Electronic Viewfinder, what you see is what you get. Changes to exposure, white balance, etc. are clearly visible, in real time, in the viewfinder or on the LCD.
The image stabilization system in this camera is a new '5 Axis' image stabilization that is built into the body -- so any lens you mount on the camera is stabilized -- even manual focus legacy lenses. It is the most effective IS I have seen thus far.
Image quality is superb, with great fine detail rendering and excellent colors. The high ISO performance is also excellent, with range extending to ISO 25,600.
If this camera tracked moving objects as well as my Olympus E-5 does, I would have not hesitated giving it a '5' Rating.
The greatest benefit is its small size and light weight. I have a small Lowepro sling bag that holds the camera with 14-42mm lens and battery grip, 45mm f1.8 lens, 40-150mm zoom, 75-300mm zoom, FL-600R Flash, extra batteries, cable release, etc. -- and I can easily lift the entire, loaded bag with my little finger! I love it :-)