It's one of my favourite lenses ever, perfect for adapting to digital, I use it mainly as travel lens on the GXR-M, had used it on the nex7 in the past, and on a 5D classic before it., it's biting sharp from 2.8 already, and gets even sharper down the road, exp. on the GXR with no AA filter, the shapness is much crisper than on any other digital adapted before.
I had 2 copys of it, sold one recently to fund some other things. I wouldn't ever part with the last remaining copy I have. besides the 90/2, 50/2, 21/2, the definite superstar in the OM zuiko lineup.
compared to todays plastic crap, this is of serious built quality, full metal, smooth aperture (8 blades afaik), also It's future proof, no AF, no electronics, just wait until sony pulls out a Fullframe nex and see what happens to the prices.
the buyer of my recently sold copy has basically glued it on the the M, the only zoom I know with primelens like bokeh transition.