Partitioning effects would increase the effectiveness of carb loading I would have thought. Basically making those carbs required for endurance sports more effective as they are drawn to the muscle tissue more effectively i.e less bloat and water which can make you feel pretty heavy and be detrimental to performance.
I don't know of any studies on it (havnt looked) but I would wager it would also help to retain muscle during/following the events, much like leucine or BCAA's.
That being said i can think of cheaper ways to do this if competing in endurance is your aim. I would gladly spend the money if muscle GAIN is the emphasis as this (to me) is much more difficult to achieve.