The AIS 135/2.8 was one of the first lenses I bought. At the time I figured it offered a bit more bang for buck than the 105/2.5, being the same price, with more reach and only marginally bigger. It was my "poor mans 80-200/2.8", with a focal length mid-way of the zoom I could cover pretty much the same as the zoom with a bit of foot work, it has the same aperture, focuses closer, much smaller and much cheaper, and probably sharper too.
A modern version with better correction of colours for digital imaging would be welcome ...