How is this compare to Nikkon Series-E 100mm f2.8 or even old Elmarit-R 90/2.8... I have few in this range (including Jupiter and Helios), and unless moving to very expensive APO like lenses, I am not able to think any greatness in this...
Not much of a deal there. The lens is an early silvernose version, single coated. That lens is no comparison the the Zuiko 100/2. I know, I've had them both.
The Oly 100/2.8 is a nice lens, but not spectacular. Not that sharp below f/4. Its biggest strength is it's size, which is about the same as most 50mm lenses. I've used mine a lot on the E-1.