In addition to the E-M1 with the new 12-40 mm (supplied by Amazon on 3 11) I had the E-M5 and am also of this already quite impressed.
What is good? The camera as a whole, focusing (better / more accurate than Canon / Nikon), stabilization (my main reason for Olympus and against Panasonic), the lens (better sharpness to the edge as the counterparts in the full frame, great idea for manual focusing with stop) , the adaptation of the beautiful FT lenses 12-60 and 50-200.
What would be better? Operation of the Nikon D800 is - subjective, for me - still so much better than the Olympus Gefummele with small knobs function. Even the menu is Olympus m. E. very askew. Sure, you can acquire, but logic and intuitive operation is different. A built-in flash would be nice to get the Panasonic indeed back.
My main criticism is aimed at the overall objectives and the pricing. The Consumer lenses from Olympus are absolute cheap plastic parts, each with even begin wise inclination to quality have to pack the horror. Sometimes I caress my manual Nikkor lenses or a Leica lens, if I want to experience the best possible contrast. Visually at no aperture sharp edge to edge (14-42, 14-150). The "middle line" of Olympus MFT (eg. The 45s or 60s) are much better, but in the case of the 60's also really expensive, and still require 50 to then for a cheap plastic sun visor? Unbelievable. The new 12-40 is high in another league as the 75er, and comes with an at least qualitatively good sun visor, finally - that gives us hope. Yet the coming 40-150 2.8 in the same quality and still affordable, and I would now almost entirely happy.
Summary of objective criticism: at the hefty prices Olympus might deliver a few more quality lenses and less turmoil in the entry-level segment.