For me the Sigma DP Merrill 2 and DP Merrill 3 were the peak of Foveon development. I loved both, although the DP3M was kind of bulky with the longer lens.
The image quality was sooooooo good. Unbelievable at that time. And the 3D and transparant effect, like looking through an open window compared to a closed one with a Bayer sensor was and still is really impressive.
You see it in the portrait shot above.
The later DP models were not for my taste. The changed the Foveon sensor and IMHO not for the better.