It's an old post, I know - but I had this s-Zuiko 100-200mm F5,0 lens with an OM2 in 1984 and used it extensively all over India during a 6 month working stay.
It fulfilled the brief of a lightweight zoom (only 9 glass elements) and delivered really great Kodachrome 64 images; sharp, excellent colour rendition and very good mechanics. I also had the 70-150 and rated this 100-200 as more useful so left the smaller range zoom behind.
For daylight images F5.0 is no problem for focus - but it was critical to keep my eye exactly on axis for the microprism screen. Off axis by a few mm was all it takes to make it darken.
Today, when I use film cameras it is for "slow" photography (akin to slow cooking) I prefer to use a 135mm or 200mm prime and leave zooms to where I have AF and image stabilisation and digital sensors.
Stick to its intended use (lightweight, outdoors) and this can be a great lens.
Best wishes to you all - Paul C