A co-worker of mine recently bought this very special lens to go along with his Nikon D90. Few days ago I had an opportunity to play with it a little.
Obviously, being a rather old lens, a lot can be found about it on the net. So I will put here only my personal impressions.
Everything just works. AF is quiet, quick and precise. The defocus control ring is conveniently placed and is very to operate. Although somewhat on the heavy side (it is after all a fast f/2.0 optic), it is only ever so slightly front heavy on D90. The viewfinder view is bright, although judging exact degree of defocus is not always so easy. But chimping is easy these days, isn't it?
This is where it truly shines. In fact, the whole idea of defocus control, where the degree of defocus is decoupled from the aperture (unlike, e.g. Pentax soft lenses, where the softness is simply set by the aperture) is just brilliant. The three dimensional effect due to play of in focus to out of focus transition can be very pronounced too.
Highly recommended in all respects. It can be used both as fast medium tele lens and as a very special portrait optic and for great many other purposes.
If I shot Nikon I would definitely get one of those defocus control lenses because I quite like the soft focus effect.