Reports I've read say it is Kodak with Jenoptic providing the digital elecctronic expertise that Imacon provided for the DMR. Like the DMR it is a 16 bit CCD sensor with a 1.33X crop factor. It is not the same sensor as the DMR however, due to needing design features to accomidate rangefinder lenses which set in closer to the sensor plane.
BTW, Imacon does not make sensors.
The ISO sensitivity ranges from 160 to 2500. The viewfinder has bright line framing for 24 through 90mm lenses ... so the corresponding wide Zeiss ZM glass can be used (like the ZM25/2.8) without an aux. viewfinder. My suspecions are that a 21mm can also be used without a aux. finder by framing using the full viewfinder window .... but that remains to be seen.
Preliminary reports from beta users say that it is very much like the Leica DMR in picture quality and dynamic range with improved higher ISO quality.
The new M8 has a different shutter than the Ms of the past. The cloth shutter has been replaced with one similar to that of the R9. 1/8000th top speed and 1/250th sync speed means fast M mount glass can be used wide open in broad daylight ... and fill flash can be more easily used outdoors with wider apertures.
I ordered mine last year and am #1 on the list of my long time Leica dealer to receive mine in early November (hopefully).
dpreview has a comprehensive technical overview of the new camera already: