Ray-traced shadows can also be used for soft shadows, it depends on the settings in your lighting properties. When you set-up a light the default is a spotlight with depth-map shadows. Usually they have a small mapsize, about 256 which you can see in the parameter tab, increasing this value to 512 or 1024 can improve your shadows. I'm not an expert in lighting or shadows, but  I'm not very fond of depth-map shadows, although ray-trace shadows take a longer time to render, the possibilties are much greater: ambient-occlusion, reflections, refractions and much more.

-How can you improve things when you don't make mistakes?