I used flavored gu (simple carb) mixed 1:3 with plain hammergel (complex) last season and had good luck. I drank a large bottle of G20 for every two regular of water. No sickness. The flavor is light and made me want to drink more than just plain water. I also threw in a bit of Extran as well - in the juice boxes. That stuff works well... I plan on trying the powder this spring.