Pros - This keyboard came out in 1998, and has aged surprisingly well. I have used it alongside much more modern software instruments, and it blends perfectly. A few of the drum sounds are VERY 90s, but I don't use a keyboard for drums most of the time anyway. Patches are fully customizable (if you can figure out how). And, as a bonus, it has the legendary M1 Piano hidden in it. Plenty of effects, and has four assignable knobs. Keybed is weighted and feels nice to play, even if it feels a little plastic sometimes.
Cons - AWFUL UI. Where to even begin with that? I have owned this keyboard for four years and have read the manual dozens of times, and haven't the faintest idea how some of these functions are supposed to be used. Patches are arranged seemingly randomly. There are 11 banks: Combi User, A, B, C; Prog User, A, B, C, Drums, GM, SFX (which are just the GM sound effects). Within these banks, there is no order. The accordion is next to a Wurlitzer, surrounded on either side by analog pulse lead/bass splits. Korg makes great-sounding equipment, but menus are not their forte. The interface takes a moment to get used to, especially if you are used to a Roland (it's very different).
Overall - If you ask me, the sound quality is worth the clunky interface and scattered patches. There are some solid sounds on here I can't go without in my pieces. If you use this synth, I would recommend downloading the Instrument Definition file found here: http://www.ugoaudio.com/korgn/