The OM 55/1.2 is soft when wide open and sharp at f/2. I'm not finished with it yet. typically $550+
The OM 50/1.8 is sharp at all apertures but has weird bokeh - probably a result of its rudimentary aperture control. That said, they can be had for about $30 and are compact, well made and robust.
Ah! A Zuikophile!
Yes, I have both of the f/1.2 lenses: The 50/1.2 and the 55/1.2. The 55/1.2 is NOT the older one with the radioactive glass element.
They are both pretty terrible wide-open, but pin-sharp at f/2.
I did a comparison of those 2 lenses with the Canon 50/1.4. I found that the Canon is faster (i.e. brighter in terms of T-stop or light transmittance) than the Zuiko f/1.2 lenses. But there wasn't a lot in it.
I also have a Zuiko 50/1.4 silvernose that I had cleaned internally and it came back in really good nick, nice and clean.
And a 50/1.4 that has SOME fungus inside but not a huge amount.
And a final-version 50/1.8, the final version they did. That is totally 100% clean inside and out.
One day I intend to do a rigorous comparison of all of them.
I like the 50/1.8 cos it is tiny (short, almost pancake-y) compared to the f/1.4 and f/1.2 versions. So more portable.
When the EOS M II comes out, I intend to get it and use it (sometimes) with the Zuiko 50/1.8 on it.