I am going to be an even bigger heretic, I shoot both Nikon and Canon, both film and dig, and I was bored and curious so I ordered a Yongnuo 50mm 1.8 to replace a broken Canon Nifty 50 (the breakage was not the lens's fault, the lens was dropped on a concrete floor when the strap broke (grumble grumble)).
ANYWAY, bottom line is I like the $40 Yongnuo better than the Canon I replaced it with. Very sharp, but what really shows is the Bokeh is MUCH better and that's one of the most important things there is to consider when buying a fast prime.
Normally, I don't shoot off-brand lenses but I thought I would throw this out there because that thing is so darned cheap you can buy it AND another prime and have the best of both worlds.
That's interesting.. the few reviews I saw rated the YN lenses rather bad, especially re: sharpness.
I love their flashes but...