50mm F/1.4 is a great lens but F/1.8 is also not bad.
I own the 50 mm F/1.8 and love it much.
Besides the slow AF and low class build quality,
50 mm F/1.8 can actually deliver great pictures and very sharp photo.
IMHO, if u really interested to get a great prime lens.
U can consider the 85 mm F/1.8.
The bokeh from that lens is really amazing.
The USM and the bokeh make it more value buy than the 50 mm F/1.4.