It's like saying "I care about milk, not cows" . I'm talking about pixel color accuracy and fake resolution. Have a look at some Sigma DP2 Merrill RAW samples (ISO 100) and you'll see what's the difference between the real 15 megapixel resolution and the fake 18 or 22 megapixel resolution from 7D or 5D3.
Foveon is another area of great hyperbole in photography. An 18 MP Bayer sensor does not have "fake" resolution. There are 18 million sample points of luminance data. And a Foveon sensor does not have 3x its pixels in resolution. 15 MP Foveon has 15 million sample points of luminance data.
Foveon sensors do have more sample points of color data, and this results in better images then a mere count of MP would suggest. That can be seen and should not be denied. But it's not the night and day difference claimed by fans. Nor will they scale to match 30-40 MP Bayer images. This is the hyperbole. Go ahead and photograph a landscape with foliage using the Sigma and a D800e and see how the Sigma fares scaled to match.
With that out of the way, I wish Foveon would have had a chance with a larger and more aggressive company like Nikon or Canon. The technology is interesting. If it could have been pushed up in MP and ISO at a faster pace it might have had a much greater impact on the market. Again, it's not night and day. But it's certainly a strong edge in IQ.
I mentioned the Foveon X3 as a benchmark for Bayer sensor in terms of resolution (per-pixel color accuracy at low ISO). I'm not saying that Foveon X3 has 3x it's pixels in resolution. It's more like Foveon X3 delivers 95% of it's sensor resolution, while Bayer delivers only 30-80% of it's sensor resolution (depending on pixel size). Sigma cannot compete at ISO 400+, it's too noisy, but at ISO 100 there is a nigh and day difference compared to 18MP APS-C and even 22MP FF seems to be not quite as good. Google it . It does scale nicely up to 30-40MP, even if it is foliage landscape. However, D800E may have the edge, but it's not like night and day difference .