I have a couple questions regarding the sensor. Is there a real noticable difference in image quality between an APS-C and 4/3rds sensor? Are the Fuji sensors a different breed than sensors from Sony and Panasonic, as far as their real world performance goes?
Everything else being equal a larger sensor will give you higher Sensitivity, less Noise, wider Dynamic Range, and a more shallow Depth Of Field.
The problem is that "Everything else" is
never equal, so we always have to compare the different systems and sensors in real use, or judge the actual results.
That said we can at least illustrate how small or big the size difference is between Four Thirds and APS-C (and also Full 24x36mm) sensors. See the below illustrations.
Of course the difference will be somewhat reduced if you tend to often crop the ends of the long dimension on the 3:2 aspect ratio to gain more of a 4:3 aspect ratio or so.
Personally I wouldn't
upgrade for the sensor size difference alone.
But if I were to buy a
new camera I would definitely go for the larger APS-C sensor over the smaller 4/3,
everything else being equal
With regards to the Fuji sensors breed, Fuji has since 1999 developed their own proprietary Super CCD sensors with a unique layout using octagonal, rather than rectangular, pixels.
But be aware that according to the dpreview link Fujifilm is this time going to put a
CMOS sensor in the X100 camera.
So far I have seen no informations about who is the manufacturer of this sensor.