I have the FA31/1.8, the K30/2.8 and the K28/2. What do you want to know???
I think, from a photographer's point of view, that the FA31 is the best choice. Of course, because it has AF, auto aperture, can be used in all program modes of your camera, etc.
The K30 is a typical strange Pentax focal length. Like the K120, which I also have. It's a great lens also, but stellar? I don't know, maybe I should do a shoot-out between the two
It has a typical Pentax K build, meaning that it's better built than the M series (more akin to the Takumars which are literally bomb-proof).
The K28/2 is a diferent beast altogether. I prefer it using wide open because of its unique ability to separate the subject from the background. This is even more evident in movie making (the K28/2 was designed by Herr Dr. Erhard Glatzel with movie making in mind, hence its nickname "Hollywood").
Off topic: look what he was awarded by the NASA: