It seems to me that you have already reached the answers that you are looking for here. IMO, the current image quality from 4/3 or APSC sensor sized cameras is capable of satisfying a lot of photographers. Certainly, resolution is more than enough for the majority of us who do not print wall sized photos, then the questions remaining regard things like dynamic range and artistic considerations like depth of field, and so on.
I do relate to your experience, as I have gone through a similar process in tha last couple of years. I have shot slide film with EOS cameras for 20 years, then I have bought a 5DMKII. Wonderful camera, that I have complemented with a small micro 4/3 system. I have tested the GH2 for a few months, but I quite never "clicked" with the camera. At the same time, the Pentx K5 was released. I always had a soft spot for Pentax and its ethos with commitment to fine prime Limited lenses. Then I have seriously considered what my future requirements would be, and opted for the K5. I simply could not justify to lug around a heavy EOS system (mind you, the lenses were heavy, not the 5DMKII itself).
These days, I can carry a couple of K5s and 3 Limited prime lenses in a small bag, the entire day. I am still learning this Pentax system, but the Limiteds are wonderful lenses, and the K5 gives superb results. To me, it is the perfect solution, and a very good compromise between a micro 4/3 sensor and a full frame sensor.