Side note, this was a nearly new (very low hours) unit from the rental place. Maybe the brakes had some issues....I don't know but they really sucked and it really took all my strength to keep them applied so the machine would not free-wheel again.
I believe something must have been wrong with your brakes. On my L35 I can bog the engine down pretty hard by applying the brakes. Stopping while rolling, etc is not an issue, but I hear your concern/fear! That would be a scary situation to be in.
As for a decision, right now I'm waiting to see if my L35 will sell or not. I can't afford a M59 without selling it first.