I've had a look at all of the Sigma samples, and while they did look initially attractive, on close examination I got the impression that there is a lot of luminance smoothing and edge sharpening going on, which gives a very odd look. I don't find that particularly a problem, but others might.
With the improvements in Bayer sensors over the years since Sigma first started with this, I believe much of the perceived Foveon advantage has been eroded. The Leica M9 uses a Kodak Bayer sensor with no AA filter and the results from that are sharper and have better colour to my eyes. This in a camera that has a RRP lower than the Sigma!
As I say I like the look from the Foveon sensor. However I don't think its "better" than a Bayer sensor, and I don't think it can be in any way compared to genuine medium-format because it just doesn't have the resolution. Yes you can upsize the files, but then you can upsize files from an M9, S2 or Hassleblad just the same. I bought my M9 because I interpolated some sample raw files up to the same size as those from my D3X and felt they looked sharper. Cameras like the D3X and Sony a900 etc. do use fairly strong AA filters, because of what they will get used for. No one who shoots fashion for example is prepared to tolerate any moire at all. Interpolating these Sigma samples up to 24MP gave me results somewhat inferior to those from my M9. So it doesn't look like medium Format quality to me.
I'd have loved to try an SD1, and at £1000-1500 I would have. Anything over that and I'll pass. What has possessed Sigma to price it as they have is a mystery to me. Most users of SD14's and 15's simply can't afford it, so thats destroying their primary market. I can't see "Pro's" rushing out to buy it either. Firstly they are concerned about price as well, and Secondly its an untried system. Sure M9's and D3X's are expensive, but Leica and Nikon have a reputation and the cameras are re-sellable at decent prices. Look at what S/H Sigma DSLR's go for.
I think we all probably realise that the 3-layer sensor is going to be more difficult to produce and more expensive, and those of us who were interested in the camera would be prepared to pay a little more. However it seems Sigma are attempting to pass on all the costs to us. They have now put themselves in an almost impossible situation. If they reduce the price then nobody is going to trust them anymore. This on top of the fact that they announced some time ago that it would be priced the same as a Canon 7D, which has really angered current Sigma owners who feel cheated, and who can blame them. If they keep it at its current price, or something similar then I think its pretty certain that they will sell very few cameras.
There's a story here and at some point in the future we may get some idea of what's gone on. To me, and virtually the whole on-line photographic community, it looks like some huge self-destruct and the beginning of the end for Sigma as a camera manufacturer. I can't see any other alternative. If they think that somehow this camera is going to turn them into a small volume, high quality specialist camera manufacturer, then I think they are wrong. I must be pretty much in their target market. I'm professional, I shoot mainly landscape for stock and I make a good enough living to be able to afford it (Though this would probably require selling my M9) However I think the results I've seen so far don't justify it, the lack of a good enough reputation for re-selling the camera don't justify it, my previous experiences with Sigma and the Foveon sensor don't justify it and finally my lack of trust in the company because of how they have misled people doesn't justify it."