I also own an i2. The presets sound superb. Excellent fidelity and attention to detail. Although I must say the i30 for some reason lacks the warmth of the i2, especially the sax sound. Most sounds on the i30 is excellent and usable.
Guitars are probably the worst sounds on thie board.
It has 18MB of PCM ROM, and I think it may be the same waves as the N1. General MIDI patches are first rate. As for the built-in styles, there are so many too choose from, and all of them sound fantastic. It sounds like an entire band, and you'd have a hard time telling differece from a REAL band. Chord recognition is excellent and much faster than on the older i-series, although I wish it was faster yet.