I'm just an enthusiast, not a pro or anything, but here are some ramblings about why I switched to Micro Four Thirds. A number of small, niggly things added together to make me start to dislike my Nikon D40. It's a bit on the old side, but that isn't so much a problem in itself. I had a couple of lenses and a flash unit. But when considering whether I needed to upgrade my body, or experiment with new lenses, got me into re-thinking whether Nikon was right for me long term. I don't like how the current split between Full Frame (Nikon FX) and APS-C (Nikon DX) has ended up disadvantaging people who bought DX stuff. Back when I first dipped into DSLR territory, Nikon or Canon were the way to go, and basically all their stuff was APS-C. Nikon called this format DX and they brought out a number of lenses specifically for it. The trouble is, now Nikon seem to be repositioning DX as an amateur format and are bringing out countless cheap slow zoomy lenses for it, and all their good new stuff - fast zooms and primes I may want to try in the future - is FX. That's fine; it'll work on a DX body albeit with a crop factor, but in making any investment into it, you have to think about whether you're going to be able to stay with DX indefinitely or if will be necessary to move all up to FX one day to take advantage of that better stuff. And if it is, it's both hellishly expensive, and you'll need to throw out all your DX lenses as they are not compatible anymore. So if my existing gear wouldn't be able to come with me through an upgrade anyway, I may as well have given the same amount of consideration to non-Nikon gear as Nikon gear when considering an upgrade. And considering how I can't afford to buy into the more future-proof Nikon FX format now, it made jumping ship tempting. My Nikon D40 has dust on the sensor. It's not a huge problem, and I can have it cleaned I know. But more would form after that, and the dust sits so close to the sensor that stopping down even to f/8 makes it visible. It made me uncomfortable choosing greater depths of field, and it's not nice to have your creativity hampered like that. Newer camera bodies have a sealed filter further in front of the sensor to throw dust further out of focus. And they have dust cleaning technology - I don't know how effective that is but it has got to be better than nothing. Another thing - I don't know if it was the mirror/pentamirror assembly or the camera design or just me, but all my pictures seemed to be tilted on a very slight angle - the same angle. Every picture I took that included a vertical line or a horizon (which is a lot) I ended up spending most of my time concentrating on getting those right and compensating for the fact that I would probably otherwise get it crooked. I can easily fix it in post, but that's fiddly. I told you these were all just small, niggly reasons - none of which would make me dump a good camera, but they at least got me thinking about what cool new stuff I'd like to own instead. I was even drawn into thinking about image stabilization, having none on my D40 or its lenses (I've had them since before VR came to so many Nikon lenses). Lastly but not least, the camera was just too big for me. It meant it was just too much of a hassle carrying it around and getting it in and out of my bag, and everything like that. I would take it with me less, and would feel self conscious with it around my neck or being in a crowd with it. And yet it's basically the smallest Nikon DSLR. I considered a Canon G11/G12 and S95 but always put it off because the small sensor size and consequent poor low light performance always worried me. Plus I wouldn't be able to play around with any changeable lenses at all; so I'd have to keep my DSLR anyway and I'd still have the problem of what to do with that. I'd heard a thing or two about Micro Four Thirds but always dismissed it since I thought/assumed it had a small sensor too, just like a G12. Then one day I was reading and realised the sensor size was actually very similar to APS-C (just a little smaller). Perfect! I thought. And they've even done away with the mirror assembly and managed to get lenses smaller and simpler, like Rangefinders! The E-P1 and GF1 seemed like great, go-anywhere, stealth (non-intimidating) but still high image quality cameras. Now I have an Olympus E-P2 and Panasonic 20/1.7 and it's great. The ability to play around with my old, M42 pentax lenses via an adapter is even a bonus. It's clearly a camera that real camera enthusiasts can play with and get creative doing so, even more so without the bulk or huge expense of Nikon FX or a 5DMkII or anything like that. It's also a just as if not more capable camera than my D40 - mostly because technology has marched on a bit since then. Low light efficiency is pretty much the same despite the smaller sensor size (though it's no match for something new like the D7000). Dynamic range is fine, color is fine. It goes up to 6400ISO if you want to push it that far, it has in-body IS, it has better autofocus (D40's was very basic, even though it was phase-detection) and has a faster continuous shooting rate. It satisfies my needs. Don't know if this rambling story is interesting to anyone, but others feel free to add your own story.