I recently moved away from Nikon. I had no issue with image quality or the product itself, the weight of the gear made it unusable for single handed use so I took the plunge and changed all my gear to OM Systems. I use the OM-1.
My favourite wildlife lens
The Olympus M.Zuiko Digital ED 300mm f4 IS Pro Lens.
The Olympus M.Zuiko Digital ED 100mm-400mm lens
gives me equivalent reach of 200 mm- 800 mm
with a x2 teleconverter a massive 1600mm