I think Tom is right here, and while I was initially reluctant to come onboard with the GXR concept I'm coming around to it. For me the key is thinking of the different modules as different cameras and the body as just an accessory common to all, like a detachable viewfinder.
When looked at like this the value proposition becomes a little different, especially in large sensor category. For the upcoming 28mm module, the combined cost of body and lensor is likely to be around $1300 Australian dollars, whereas the competitors are either slightly cheaper (Sigma DP1, $899) or much more expensive (Leica X1, $2600). Even the Fuji X100 is rumored to be around $1300, although nobody really knows what it will come in at.
Some have made the case that it was stupid for Ricoh to lock the sensor and lens together, as you have to buy a whole new assembly if you want to upgrade to keep pace with sensor developments. Well, in the case of these other cameras you also have to upgrade the lens to get a new sensor, but with these you also have to upgrade the rest of the camera.
The other option is of course micro 4/3, but I think they are actually a different category. To me, these are really smaller versions of a DSLR, whereas the GXR is more of an APSC fixed focal length compact camera which happens to have the option of being used as a small sensor compact.
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