While I used the Nikon D300, I had an 85/1.4 AI-S and an 85/1.8. In terms of size and weight, the 85/1.4 was a monster. I’ve later tried to use it with the Olympus E-P2 and an adapter, but I soon lost interest. The adapter added to the length, and the whole thing was pretty unbalanced.
The 85/1.8 was much smaller and lighter, but wide open it suffered from purple fringing. It was an old design, clearly not made for digital cameras.
Why do I mention that? The reason is, that in terms of equivalent focal length at 35mm they are more or less the same. It’s the classic portrait lens.
Of course the Olympus 45/1.8 can’t match the mighty Nikon 85/1.4 in bokeh wide open. In fact it can’t even match the Nikon 85/1.8. It does not matter though. If I want something close to that, I just use the much bigger and heavier Olympus 75/1.8. In terms of bokeh it’s wonderful, in terms of shallow DOF it’s close but not there. It is still smaller than the 85/1.4 AI-S that I had and it weighs 300g. That’s half of the Nikon. Of course both Olympus lenses focus extremely fast, none will ever show front- or backfocus. That’s one of the big advantages of mirrorless cameras: focus is always accurate and you don’t ever need focus adjustment settings.
But really, most of the time I am not interested in shallow DOF at all. I can have it if I want to, but if not, I enjoy a trio of featherweights, for instance 12/2.0, 25/1.8 and 45/1.8. That’s one main reason why I always come back to this small, sharp and precise lens.