If you care about rendering times, buffer shadows is awsome. Its real fast and you get heaps of control over what objects are in the “shadow cone”. Thus its easy to optimise a scene for perfomance. this can be important for animations, where blender renders are not so good at cacheing previous frame calculations.
For my own, I often use buffer shadow, and I think that it allows much more control on the light and shadow parameters, with a much shorter rendering time.
Raytracing gives hard shadows, which look not very natural.
I also think that a feature like buffer shadow would be very usefull with ordinary lamps.