I have to admit, that I miss DSLRs from time to time, but I don't miss the weight and the technique, I miss the image quality of full frame. Before buying my Olympus E-M5, I considered buying the Canon 6D. But at the end of the day I added the weight of the lenses I would need to do what I was doing with my E-PL1 and bought the E-M5. At least that were my thoughts about half a year ago.
The Olympus E-M5 is a fine camera and it delivers good results, but only with my best lenses. However, the difference to my E-PL1 is not as big as I thought in most conditions apart from high ISO. I like having more dynamic range and less noise at high ISO, but I can also see relatively much noise at ISO 200, even in good light on sunny days. Generally, with lenses like the 12-50mm or 14-150mm the difference to my Canon G12 is astonishingly small, too small.
I am not sure, if I have bought the right camera. I like its size and I like its image quality with my best lenses, but my bag would not be that much smaller with a Canon 6D, the Canon 2.8/40mm and the Canon 1.8/85mm, which would be sufficient for most of what I do with my E-M5. For my hiking trips I could have continued using my E-PL1 or my G12.
However, there is one more point: Olympus has risen the prices of their lenses significantly. The price of the 75mm has been risen by about 20% and that's just one example. The rumored E-M1 will cost most probably significantly more than the E-M5 at its launch and I am afraid that it might cost about the same as the Canon 6D. I would not buy it anyway, because I bought my E-M5 only half a year ago, but had I foreseen Olympus' ridiculous new prices, I hadn't bought an E-M5, I would have bought the 6D instead. I am afraid, that µ4/3 could fail because it's much too expensive. Both companies, Olympus and Panasonic, have significant losses concerning their photo business for some time now and I am not wondering why.
That's why I understand people who want to go back quite well.