When upgrading from 7D to FF (5DMkII) I had a limited set of lenses that fitted the new camera. So I bought it with the 50/1.4 and was pleasantly surprised with the IQ. The copy I got does not resemble at all any of the negative ratings found here. Even at 1.4 it focuses sharp both near and infinity - and that with AF no manual override.
As being one of a few lenses I had initially for the camera I used it extensively and it was a nice experience going "back to basics" with only a 50mm at hand. I am pretty picky with sharpness and this particular lens performs so well that I do not feel the need to take several shots on the same subject as I know normally the first will be focused spot on where I choose. It also produces a nice soft bokeh and is capable of nice 3D-isolation. I cant find any flaw with this lens, the only thing that could improve is the build. But this one is still miles ahead of the 50/1.8. I use no filters, the lens hood is protective enough. And the hood construction is good - as opposed to the flimsy mount Canon makes for eg the 85/1.8 or 50/1.8.
So either I am lucky, or theres bad copies out there and/or perhaps handling issues for some users that dont realize just how short the DOF gets.