1) I own already too many cameras, DSLR (Nikon), MF (Hasselblad), small cameras like EP2 and several Digilux 2, 3 etc.
Each system caters to a different platform and specific use.
I was bitten by the Sigma Foveon bug when I picked up a DP1 for a decent price. While the DP1 is horrible as a camera to use, the images this little P&S could handle just got me very interested in the DP2s - they are two very different cameras.
I use Nikon FX for my SLR kit, the Micro 4/3rds system for a compact interchangable lens system kit (huge difference in size and weight compared to my Nikon kit), had an S90 for a P&S, Contax G2 system for RF, and a little Contax T that has served me well for 25 years. Had an LX3 and had been thru the Canon G series before the S90.
Ever since I got my hands on the DP1 and more recently a DP2s, my Nikon and Panasonic/Olympus camera's have not been used much.
2) Will the IQ be really better than the EP2?
I use the GH1+14-140 and EP2+7-14mm. It's almost like comparing apples to oranges. The EP2 offers very nice typical Olympus colors and the Olympus/panasonic lenses are very good - sharp, contrasty, and compact. The 7-14mm f4.0 is my absolute favorite. However, foveon has a little bit different flavor to offer and while both are quite good in their own way, I prefer the look for the DP2s files. Shooting at ISO 800 or ISO 1600 (B&W or color), you can actually get a bit more detail from the foveon sensor than you can from the M4/3rds sensor
3) How difficult are the Sigma RAWs to develop - is Adobe Camera Raw supporting these files? What are post processing SW - I think I will not like the Sigma SW.
I have been using Sigma Photo Pro and while this software is extremely limiting compared to CS5 or even Bibble, it does a good job with the X3F files and is quite simple to use. You can always post process more once you are done with the X3F in SPP. ACR and Lightroom (I think) support X3F files, but when SPP does such a good job, why bother with other software.
4) What are the weak sides of this camera - be honest please!
AF is good and the lens is impressive, but overall it is a slow camera compared to say the Canon S90. It is no match for the AF speed of the GH1 with panasonic lenses and is not even worth comparing to an SLR in terms of AF speed or overall operation.
This is the camera you want if you have time to think and get the shot you have in mind. Not suitable for moving subjects unless you are into shooting snails or maybe a wounded rodent that has a limp. Absolutely impressive for outdoor daylight use and portraits if your subjects can stand still. Did I say the lens is absolutely amazing - right from f2.8. While one can't compare a 28mm f4.0 lens to a 41mm f2.8 lens due to the different focal lengths, if you had to choose one based on the better lens, without a doubt the DP2s has one of the best lenses used on a P&S.
I am looking forward to trying out the time lapse feature the DP2s offers.
Metering is quite accurate, but as with most digital camera's, the WB settings need some tweaking from time to time. I have not had issues with the magenta or green casts that have been mentioned in the forums from time to time. I only shoot RAW and maybe the cast issue is a JPG deal.
5) What if I really like the Foveon results, I will maybe then also go for a SD15 - I really fear!
As always best to wait a while to let the early adopters help sigma get the kinks out of any new camera. But damn, it seems like a pretty decent camera.
6) Will there be a FF Foveon sensor and DSLR in some reasonable time?
Welcome to the "Lets all hold hands and pray for a full frame foveon" club.
Here are some snapshots from the DP1 and DP2s - mostly street graffiti - the level of detail in the full size images is stunning.