K/M/A f/4 100 mm macro vs FA-100 f/2.8

[Toralf Lund]

I'm still sort of casually looking for a real macro lens... Just 
wondering, how do you people reckon the old f/4 Pentax macros compare to 
the newer FA-100 f/2.8? (Just came across one of the former class for 
sale; not sure if it is the F, A or original K variant - I'm assuming 
these are all based on the same optical formula.) Also, how much of a 
point is AF for macro work? I mean, does the autofocus work very well on 
macro range?

- T