Hi Chris I changed to the E510 (not much difference from E520) from a Nikon D200 over a year ago. My main reasons were overall weight, in-body vibration reduction on the Olympus, and the presence of a dust removing facility. Image quality on the Nikon was always reckoned to be pretty good, but for me the pics from the Olympus were every bit as impressive, if not better. A lot of my photography is indoor, low-light, without flash, and noise has never been an issue. The Olympus lenses are brilliant - and feather-light compared to equivalent others I've had. I bought an E-3 when that came out - so I've got the weight back now in one respect - but the difference is that, with the extra speed and range of 4/3rds lenses, and their low weight, I can still take an effective outfit everywhere. I'm going to the Isle of Man in a couple of months to photograph the Manx GP. Taking an appropriate Nikon outfit on the bike has been really daunting in the past. With the Olympus it's easy. Incidentally, I blow up my best pics to suit some 800mm X 600mm frames I have. I think the quality is stunning. To my mind the 4/3rds IQ/noise problem is a complete red herring put around in forums such as this - a sort of mantra - say it often enough and it'll be true. Maybe that's why Olympus users get so worked up about it. It's a fiction. I wouldn't let it worry you. I'd recommend this system 100%. Hope that's helpful.