I have been through 3 50mm lenses ever.....and all I had diffrent thoughts about it.
My first was the nikkor 50mm 1.4, looked to have been made in the 1980's. At first I liked it, but its focus ring lacked that feeling of presicion and after taking it apart to examine the elements I found not only the apeture design is poor and weak, but there was oil in it.
So I got rid of that and I found a backup that only costed about 6 something dollars (3 lenses for 20$) from a box of trash heap lenses....I was amazed to find this in such good mechanical condition (but horrible cosmetic condition).
It is a Super-Multi-Coated Takumar 50mm 1.4 That puts the lens made around the early 1970's. The lens looks like its been through world war 3 but the lens works so well that I use it for pretty much anything. It is soft the first 2 stops but once you break the 2.0 barrier its as sharp as one can have. Only problem with the lens is the left hand focusing which throws me off sometimes, and the shallow DOF combined with the really bad viewfinder of the 10D (fault of the smaller mirror/sensor) keeps me from focusing as well as I want to.
Thats a recent picture with the lens, shot I think at most 2.0, but I doubt it. No sharpening work done, only color work.
Those are two more, the water one you can tell I missed a little with the focus, showing what I was saying of its difficulty, and the second one is a stopped down shot, I dont know what apeture though, exif cannot save info on a converted lens.
And the last lens I used was the canon 50mm 1.8, which I liked...nothing else to say about it.