After a recent, rather arduous 8 day backpacking trip into the Sierra's- with most travel above tree line and temperatures on the warm side, I can say Nuun has been very good to me.
I was putting a Nuun Sport tab every other 16 oz bottle (one straight water, the next water w/ Nuun). Late afternoon I would mix in a Nuun Endurance in the same bottle. In the evening at camp when my buddies were heating water for tea, I also heated water for a Nuun Recovery (you can drink it cold, but was actually pretty good warm!).
Knock on wood, I never suffered a single cramp. I was good about keeping up with my hydration, but as much as I was sweating, I'm sure I was also losing electrolytes.