I got the FD 50mm f/1.2 ages ago but never quite got around to modifying it for native EOS use. Ed Mika has recently launched a range of mount replacements so I ordered one. Fitted it in 10 mins and just gave it a quick go.
The FD lens is fully manual of course. It has an aperture ring, and a generously ranged focus ring. The adapter comes with a chip so the body will recognise it and store 50mm f/1.2 in the exif, and also helps allow the semi-auto modes to function.
To put expectations in context, this is not the L version. At the time I got it, it wasn't much more than the EF 50mm f/1.8 II new.
f/1.2 is quite fast, so even with current indoor lighting I was getting to 1/160s at ISO100. I haven't given it a critical sharpness test yet. It isn't as bad as feared, exceeding that of budget zooms already. Bokeh seems reasonable, with a smooth rear transition and more nervous front transition region. It does suffer from moderate longitudinal CA but that's not unexpected.
Overall I think it might be better than expected. I'll have to give it a harder workout when I get home. Note while the FD lens supports full frame, due to the ingress of the rear element it is claimed to hit the mirror of the 5D2 unless focusing closely. There is a workaround of using it in live view only, where the mirror is already out of the way. It isn't a perfect solution but the best that can be achieved while keeping infinity focus and without requiring corrective optics.
_________________Canon DSLRs: 7D2, 7D1, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 10-18, 15-85
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 50/1.4A, 150 macro, 120-300 f/2.8 OS
Compacts: Sony HX9V, Fuji X100.