e-Gel is doing a perfect job in keeping me re-fuled and highly energized through long endurance events. I just completed Half-Ironman distance event, where I consumed 12 packs of e-Gel. I felt energized throughout the event, and had no side effects whatsoever (cramps, stomach issues, etc.).
I am also using e-Gel on my long training runs and it is proving a reliable and effective product.