Would a canon 50mm f1.8 be a good addition to my kit?

I have a 40d with the 17-85mm is lens. Ive herd the 50mm f1.8 is an amazing lens obviously for DOF and sharpness. is it a good addition to my kit as i already have this focal range covered. I already have a telephoto so im not that intrested in alternatives just this lens thanks.