In article <4aq11j$p9o@agate.berkeley.edu>, rfung@uclink.berkeley.edu says...
>I am considering purchasing the Sigma Macro 2.8 90mm lens and wondered >if anyone has any opinions or experience with this lens. (..)

Durn good lens! One of the few off-brand lenses that I like. I tried
two, and both were excellent. Also, they come with an achromat that
is great with a bunch of other lenses for quick, compact, and easy
macro, or to get unusually high magnifications sharply (even with video!). The Sigma achromat plus Nikkor 200mm f4 compact (not macro)
at f11-16, plus TC200 or PN11 gets you a very nice, very sharp 3X magnification macro rig. The 90mm Sigma macro is unusually compact
and light - a nice lens.
Hope this helps.