It is a gorgeous lens. If you can live with the small F/3.5 aperture, it is an amazingly sharp and contrasty lens. When I need to travel light, I will prefer it to my Planar 100/2.0. In broad daylight, it always produced crisp and saturated transparencies. In lower light, it still reproduced the subtle shades that make those Zeiss lenses so remarkable.
My ideal field equipment comprises a Distagon 25/2.8, a Planar 50/1.4 and either a Sonnar 85/2.8 or 100/3.5. They all have the same filter thread and roughly the same dimension (the 100/3.5 is slightly longer, but not by much).
If you can find a used one on eBay or elsewhere, I think it is a real bargain.