Hi Steve,
I have an M100. The acceleration when set to the quickest setting (very fast I think it is) is amazing. It seems to go from half to full throttle in less than half a second. Impressive to see.
I had mine set to fast when I first put it in a plane. It would flame out every flight. I would take it up resonably high (cause I knew it was going to stop plus I was trying to diagnose the fault) and just cruise at half throttle. Every time it would flame out.
I was advised to put the acceleration to normal which I did. No flameouts since and I now have about 20 hours on the engine.
As a side note, I now love this engine. Always starts nice, runs perfect and is good on fuel. It looks good as well which is a bonus.
My flying site where I had the flame out issues was about 750 meters above sea level. Low humidity with ambient temps in the hi 20's (degrees C).
For me the normal acceleration curve is fine. Faster than my other turbines. It would be nice to run it on the fast or very fast curve but I am not willing to risk it.
Paul.