Originally posted by thibs It is no replacement for the FA50, it replaces the FA*85/1.4 and is priced as such.
Although I agree this new lens is intended to replace the FA*85/1.4 (full frame format for film), its focal length and max aperture is damm close to the FA 50/1.4, so yes, it better be a damm good lens with which you can notice with bare eyes the quality difference with the FA50/1.4. I say that if you need colimators, microscopes, analysers, or any other "image analysing device" to tell the difference, then the price difference is not worth it.
Of course, this is purely from a practical point of view (that is, picture taking!). OTOH, I guess there are many Pentax enthusiasts that will go for it for other subjective reasons, as pride, collector's item, brag about it or whatever. For me, its about the pictures. Period.