Imagine what you could do with your mixes if LP MB had a sidechain input assignable to only or two of its bands... ducking only the mids of a guitar under the vocals is one idea... Or ducking only the low-end of a bass under the kick... I might be misinformed, but I do not know of any plugin that can do that.
 
Anyone of Plugin heaven making notes? :O)..

PS, yes I know one can create a Xover with one buss ducking and the other not, but this would be cooler!