The lenses are extremely, extremely good. Top-tier Zeiss rangefinder designs. The 45mm f/2 is acknowledged to be among the sharpest lenses of the film era. It presents hardly any aberration of any type when shot through a 24mp mirrorless camera wide open. It's also extremely compact. To accomplish the same thing nowadays companies produce 12+ element primes to correct everything which also lower transmission. The 45mm f/2 is a six element symmetrical design.
The 90mm is a great bit of fun with great out of focus areas, and an 8 blade aperture. Does require stopping to f/4 to completely remove longitudinal CA.
The wide angles are all also excellent symmetrical designs. Unfortunately you need to use inverted macro filters on them with when adapted onto digital sensors.
On top of this, the entire system uses a screw mount to provide autofocus, so the lenses can be adapted, with autofocus to other mounts.
My dream is to own these lenses and have them adapted to Sigma's upcoming foveon camera.