1. Newest Quattro sensor technology it's not original X3F Foveon technology, so Quattro by the old Sigma users is regarded as denying all the benefits that gave this technology superiority over the Bayer CFA (unique analog feel, deep smooth tonality and microcontrast).
2. Original X3F technology died after the amazing Merrill (SD1, DP1M,DP2M,DP3M).
3. Quattro technology gave Sigma possibility to "cut a little" big data flow from with the new sensor, but it will be always bigger then in the case of Bayer sensors.
4. Quattro sensor technology introduced luminance noise problem at ISO100 which wasn't noticable in older sensors, and this is really big step back.
You can see this noise even in highly saturated with light scenes which were regarded as ideal lighting condition for Foveon sensors and gave them unbeatable analog feel which you can hardlly* get with Bayer sensors.
Sigma tried without succes to tackle this luminance noise with software changes but after 4 years it's still there, even in Quattro ASP-H, because it is hardware based from beginning - sensor architecture.
5.New Sigma camera sensor will be just a iteration of Quattro technology, with minor change, now the "green" layer will be divided on 4. (SDQ has blue layer divided on 4 lower resolution parts). See Sigma patent which was published by Japan patent office couple months ago.
6. Quattro sensor also lost microcontrast adventage and introduced - real - lower DR in terms of analog feel in daylight pictures (don't look at studio tests, it's not representative in case of Foveon technology for many reasons.)
7. Sigma cameras will not be demons of speed and suitable for all environments usage by many years ahead. (Until they will not use new light sensitive metamaterials on Si substrate).
8. It will not look as Leica rangefinders, they showed from many years that theirs design strategy is different.
