From this guitarist point of view, the M1 is still a great synth. I bought one some years go and I don't regret. Very easy programming, some great sounds and very well built. My band mate owns a O1W/FD, which has better guts, but the M1 has its charms. Only 16 voices polyphony, 8 midi channels (half of the 01W). The internal sequencer is but a toy.
There is a manual at http://webcoast.com/drevil/korgm1manual
At this site there are hundreds of patches but maybe only 5% are worth.
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