Samples with and without vibrato are both useful. Using a synth's LFO (controlled via the mod wheel) does not yield a realistic vibrato. The best way to get a realistic vibrato is to have it in the sample--in which case it is difficult to control. I do think the SD1 would be better off with a set of samples without vibrato that are used for general midi playback. But, overall, I think samples with and without vibrato should be included in a synth.