In article <4gk7nm$dfq@newton.fgg.eur.nl>, Dieleman@cid.fgg.eur.nl says...
(....)
>Now my question: has anyone experience with the Nikkors 2.8/20 or
>3.5/20 (52 mm filter thread) vs. the 4/20? Is color fringing in the
>corners less severe with this lens? The 4/20 doesn't distort too
>badly; how do the 2.8/20 or 3.5/20 compare to the 4/20 in this
>respect? What about other optical performance aspects?
>Please don't direct me to the "subjective lens test" overview. I know
>where it is and that it says to avoid the 4/20 and 3.5/20 in favour of
>the 2.8/20. Still I'd like to hear from someone who can compare from
>his or her own experience.

What do you think the "SUBJECTIVE Lens Evaluation (Mostly Nikkors)"
is based on? It is based on a lot of experience with lens comparisons.
To answer your question: Nikon took a while to get the 20mm
focal-length optics right (if one discounts the very good 21mm f4
non-retro very early design), but when they did, they did it with
a vengence - the 20mm f2.8 Nikkor (by f5.6) is better than most other wide-angles Nikon makes, which is saying something! Why bother with
the other Nikkor 20's (unless using 52mm filters is REALLY important
to you)? There are no other advantages. The best sample of the f3.5
compact version can be reasonably even in sharpness across the frame
at optimum apertures, but is never zingy sharp. The 20mm f2.8 is
crisp and nice center to corners by f5.6, with even illumination and
little flare and distortion - and it is compact, sharp over its whole
focus range, and not horribly expensive. How can you beat that?
For those who would like to check out the "SLE(MN)" (which does
include some lenses other than Nikkors [that fit Nikon] and which
checked out reasonably well):

D. Ruether's "SUBJECTIVE Lens Evaluations (Mostly Nikkors)",
which includes a listing of all Nikon SLR lenses ever made (with a
subjective evaluation of many of them, a general description of Nikkor
lens performance characteristics by lens-type groups, and comments on
particular lenses when the general descriptions plus the subjective
evaluation numbers are not sufficient to describe performance),
can be found at these sites:

-- Jan-jaap Aue: (nice text format)
http://www.phys.rug.nl/mk/people/aue/nikon/david.html

-- Bo-Ming Tong: (go to end of long article, plain text format)
http://www.cs.arizona.edu/people/bmtong/photo/nikon.faq

-- Quang-Tuan Luong: (plain text format)
http://robotics.eecs.berkeley.edu/~qtluong/photography/35mm/nikon-neuman

-- Niklas Nikitin: (nice table format)
http://www.cs.hks.se/~nicke/private/photo/david.html

Hope This Helps