A very interesting observation here; if you watch the great West Indian bowlers, when they ran in to bowl, they looked like guys running naturally, like a good distance runner, and would then add a natural bowling action at the end of it. They rarely broke down, retained exceptional control, and hit higher average speeds than most bowlers could dream of. You could call this the advantage of a lack of coaching.
Too many bowlers have run ups that look nothing like any other kind of running based activity they would ever do - be they massive curves, arms thrown out at ridiculous, sometimes perverse angles, or effete hand movements. Sure, these have an inherent rhythm for the individual bowler, but because of their idiosyncracies, they go wrong too easily whereas your West Indians greats had nothign to go wrong because they were *just running*
What to learn from this? As Nick says, the key is to be at your maximum rhythmic pace as you enter your delivery stride. What you need to do is find the most comfortable way to get to that pace, preferably in a straight line...