I've recently made up my mind that I'm going to stay with m43 mirror less cameras and probably won't get a dslr anymore. Since photography is just a hobby for me, I don't need to carry around a large camera and lens combo. I always leave it at home anyways so it hardly gets used =/
I sold my 50D few years back and got my first m43 camera, the GF1. It was nice and compact and performed fairly well. After a while I missed the performance and IQ of a dslr. Ended up selling the GF1 and some lenses and got a Nikon D7000 this time. Had it for less than a year before I sold it too and went back to m43. Again, the D7000 just sat at home as I didn't want to carry it with me. This time I got the Panasonic G3 and Olympus E-P3 which was quite good, quick AF and high ISO performance was pretty good (on the G3, not E-P3). But then I heard about these small mirrorless cameras with APS-C size sensors, so I looked more into it. First I tried the Fuji X100, but was disappointed with the sluggish performance compared to the m43. Then I read about the Sony NEX-7 and was lucky to have bought one late December last year. Used it for a little over two months and just couldn't get over the poor low light performance on the NEX-7 (with the Zeiss 24mm 1.8 lens). My E-P3 performed better in the same low light place whereas the NEX-7 could not lock focus at all. Also the lack of lenses from Sony made me started looking at the m43 again. Then comes the E-M5 which seems to perform quite good from what I've seen read online and it also has features that I want where the NEX7 lacks. Sold the NEX7 and now waiting for the E-M5.
I figured now the newer m43 cameras has gotten a lot better and IQ is pretty close to what I've been missing before, I'm going to stay with m43. Also now there are quite a few quality lenses available for them which makes it even better. While I have owned those previous mirrorless cameras, I've taken them with me almost everywhere I went. Don't think I'll regret it at all lol