The new boxes from EMU give me purple or yellow flavors. They have some killer grooves built into them and are expandable to be just like the other box (just add chips) and then some. They have a sequencer built it (great cause I need one to take home for portable work---boy I miss my Korg).
I adds spice to an existing sound set or MIDI rig and sounds decent. Best of all for this thread, all the knobs are MIDI friendly and assignable. You can also create blank control patches that work just for the other MIDI stuff one might be trying to lock into like the CW stuff here.
Sound.
MIDI integration.
Drum pads, and touch pad give me the ability to hack out those drum tracks at the desk with out having to swing over to the keyboard.
Everything a man could want and it makes the desk look mighy fine. Cool.