I personally love some of the ethnic libraries from Best Service (Persia, Dark, etc), but the actual Best Service Engine is just not that great of a GUI. It feels and looks like something out of the late 90s, too small text (where's my magnifier?), mini tiny checkboxes and an unnatural way to turn knob values with the mouse. (as in, you have to draw a circle with the mouse around the knob, and not just click and use mouse vertically)
The Engine is not doing the amazing libraries justice.