"According to a paper by the Foveon guys, the sensor does not suffer from "color noise" (actually color aliasing)."
This is not correct.
The Foveon colors suffer at high ISO because there is a lot of common mode information in the color channels. This requires more amplification to extract chroma information. When the signals are small, the noise from this amplification noise shows up as hue shifts in the form of blotches.
The up side to this seems to be that the sensor is equally sensitive to all colors whereas the bayer approach favors the primary colors of the array. My Pentax K5 produces images where the greens tend to all look like the were all painted with the same color brush. The highlights lose saturation before clipping also. This is why some people have said the colors look "thicker" in the foveon images.