I have just read up on digital sensor and pixel size (a bit of "leisure" reading for me, these things are certainly not new): Clarkvision: Does Pixel Size Matter It was not specifically written for 4/3 sensors, but I found it quite well written in explaining the physics behind digital sensors. It also cleared some of the myths I fell into. I have seen posts of people hoping for a leap in IQ with the next gen of 4/3 sensor, but as technology is at the moment, I think 4/3 sensors are at the "optimal" point already. Some points being: Signal-to-noise ratio is directly linked to fill area for photon collection on the sensor. Dynamic range is related to area and the capacity of a potential well. It is a ratio of the signal divided by the noise (mainly readout noise). The pixel size at around (my guess at ~5 microns for 12mp 4/3 sensor) is at the optimum, taking noise, dynamic range and resolution into account. The area that can be improved on (without breaking the law of physics) from my understanding are: quantum efficiency (converting photons to electrons), fill area % and readout noise (possibly larger electron "bin"). I don't know how close to the phyiscs limit the current 4/3 sensors are though. Either all this, or bring out some super fast lens.. but I need to read up on lens design before I understand why they can't get a f/0.5 20mm pancake out. In the end, is 4/3 good enough? I certainly wish it performs better in low light (say a dimly lit restaurant). Anyway, still love using my GF-1. Just throwing this out there (and maybe get a PEN with VF2)! P.S. I found this right after reading the above: http://www.wrotniak.net/photo/43/sensor-size.html As I understand, all things being equal, 4/3 sensors are pretty similar to APS-C sensors.