I got rid of my 50/1.8 and replaced it with a Sigma 30/1.4.
The fact that the nasty nifty is mechanically a plastic horror is just snobbery on my part, but I found 50mm is an almost useless focal length on a crop camera.
Very happy with the Sigma 30/1.4 - at least I've used it once or twice. But depth of field at f/1.4 is impossibly thin for a lot of things. I can see myself selling it eventually. My 17-55/2.8 IS is just so much more useful, though to be fair to the the chunky lil siggy the 17-55 replaces most lenses