Korg fan,
sampling or sample loading is important because expands the sound palette of your instrument. I am currently trying this feature on the 9000 pro, but have to say that the sample handling ability is kind of raw, compared with a real sampler: you cannot layer two sounds with a velocity switch (not to mention a crossfade), there is no autoloop feature, you cannot apply an ADSR envelope, etc.
I will experiment with my SD1 as soon as I can and will report, if you are interested.
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.