I use nunn as well. Maurten is a much different product. Nunn provides 8 calories per 16 oz and Maurten provides up to 320. Nunn provides hydration, Maurten provides hydration and calories for sustained energy.
I've used them a lot. I regularly go on long bike rides (100miles or more) and find them to work but the fixiness sometimes upsets my stomach. I find them good if you aren't needing the calories or sugar. If I want to lose weight I'll use Nuun instead of Gatorade or a similar sugar drink that has electrolytes.