I've had a 50/1.2 and thought it was tough to focus, but that was on a f4s with the standard non-split viewfinder. A split viewfinder center would make things a little easier. I mostly relied on the focus indicator LED which was sorta a slow way and not as accurate for close distances at 1.2
I've also had the 55/3.5 micro, 50/1.4d-af, and 50/1.8d-af.
The 1.4 and 1.8's that I have flare easily with internal reflections if there are very intense bright spots in the image (like car headlights or floodlights in night photos) Otherwise they are very nice and have smooth bokeh when widish open.
The 55/3.5 micro is a nice to focus manual lens. It focuses quick and in a short distance as most of the focus scale is for macro use, not normal distance stuff. It doesn't flare as bad, but isn't bright for existing light night/indoor use like the others. It has a very impressionist bokeh (not buttery like a 105/2dc or portrait lens, and not all crazy cubist looking like the 60/2.8d macro) at modest stops like 5.6-11.
Someone was asking about a pancake.... I have the voigtlander 40/2 sl2 and it's almost a pancake and is fantastic in construction and image quality.