Having had the opportunity to use, borrow, and gig with one on a few occasions (but sadly not actually own one), it's been very hard to return it. It's a stunning keyboard (even compared to the later Kronos) and is truly jam packed with tons of extraordinary features. The user interface is what makes it for me - having everything easily accessible on the touch screen. The number of different synthesis engines and the ability to combine them in the standard Korg Combis can make for the most gargantuan layered effects (at the expense of polyphony of course), but also some brilliantly practical splits across 88 notes. Then there's the Karma engine, sequencer, arpeggiators, and the HD recording facilities. The sound quality is also superb. Only problem I've encountered (and I've heard this has happened with other Oasys's (?!)) is that occasionally the touch screen would become unresponsive and require re-calibration. Aside from that, this is quite the majestic instrument.