I thought my 50mm f/1.8 is already sharp and has good bokeh. This lens is even better than the 50mm in sharpness and bokeh. The fast and silent focus is a plus.
I don't have any other lenses to compare to for build quality. Among kits lens from my rebel xt, 50mm f/1.8 and this lens, it is very obvious that 85mm has the best build quality.
I got mine used and it makes the value of this lens is even better. But I won't hesitate buying this new.