Well you can shoot them in Apature priority, on most of the M4/3 and similar set ups with an adapter so thats keeping the demand up somewhat, that and the OM line up had great great glass and muilti coatings. For the current out lay they are bargain for the quality of the glass your getting so long as you do your homework and are not getting the kit glass and getting the better ones. IIRC the 1 of the Really fast prime Telephotos ( the 250 F2 or 350 f2.8) were just recently (last decade or so) retired form NASA from orbital photo duty on shuttle missions as the sharpest lens they had ever tested....
Good OM glass referance page
Good OM glass referance page
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