i used the nikon 50mm 1.8d with d5100 and d5200 with doesnt have the motor, and it was a pain
The Nikon d5100 and d5200 have small and dark penta-mirror viewfinders... I'm not surprised. The 6D however, has a large and bright penta-prism viewfinder, add a precision matte EG-S screen into the mix and manual focus is easy and fast
And as with anything, you have to practice. I don't miss my AF lenses at all, I don't have any for my 6D anymore. Unless you're shooting a fast moving subject MF is very easy imo.