I have the 50mm 1.8 AF-D and love it. Never had the 2.0 but did have the 1.4. Both made great negatives.
The biggest reason I sold the 1.4 is the 1.8 has AF and I couldn't see any significant difference in a print.
Plain and simple, if my subjects are fairly close to me and mobile, as most are when I'm shooting 135 with a 50mm lens, then my old eyes greatly appreciate AF when I print.
My FM2 is feeling a bit neglected too as of late.