It would be interesting to know if the S3 can read any of Korg's other PCM cards. The Wavestation EX and AD can read M1 cards, for instance. I know that the S3 cannot read Wavestation PCM, and vice versa. Let me know if you've tried anything. Important information about using cards in practice is contained in the file 'Procedures and problems using PCM and Program cards'.
Sounds range from rock through to electronic through to ethnic.
The instrument's sample capacity can be doubled by making use of the two PCM ROM card slots available on the rear panel. No internal expansion is possible. This page includes full listings of all the S3's internal and card waves, as well as my opinions on the merits and usability of each wave. Also included are some audio files of some typical sounds found on each of the cards. All of the audio files use just the S3's sounds and built-in effects.