For me? I care mainly about 2D and 3D scatter plots of large datasets. The GPU acceleration and automatic subsampling means that animated or interactive scatter plots of large amounts of data (for me it's language vectors) is super easy and fast rather than slow and crappy with matplotlib...

(I think matplotlib has an openGL backend that slightly improves but doesn't fix the issues with matplotlibs handling of large datasets)

Bokeh is also made to create embeddable, interactive plots for html/js. You can create quite sophisticated graphics with it from the backend alone. (We use it for web apps at $WORK)