It has an extra pair of outputs, and the effects routing is configurable, parallel or serial. Two slots for PCM and program cards. Some of the sets you can buy are actually quite good. The sounds are pretty much unmistakably Korgish, clear and atmospheric. It seems to be reliable.
Users are usually capable of replacing the backup battery themselves.
Mine was dropped during shipment, and there is a very minor dent on the back corner. It's very solidly built, with the faceplate being milled anodized aluminum. It does look like a tank. Without the manual the 6 buttons korg gives you to control the rack unit would be hard to figure out because you have to push them in certain combinations to do different things. 6 This unit would be good as an additonal sound source for a keyboardist that has a midi piano and wants some additional rock, jazz, and new age sounds.