Like any food for hard riding, HEED takes some getting used to. If your usual sports drink is sugar or HFCS-based, then swapping abruptly to HEED is going to give you some gastric distress, since your gut isn't used to the complex sugars used in HEED. Several of us were sucker-punched pretty hard on a century ride last year when you train consistently on a sugar-based drink; then suddenly the only thing available at the rest stops is HEED. I have never cramped as hard or so badly as I did on that ride, and the only thing I had changed was drinking HEED instead of the usual stuff.

That being said, I like the taste of HEED, especially the orange and lemon flavors, but it doesn't set at all well in my gut. I did the same ride this past summer, but carried my own mix (Nuun, and Arizona Green Tea mix) left the HEED alone, and just mixed my own stuff from plain water.

HEED is one of those things that if you plan to ride hard and long with it, you need to be drinking it on a very regular basis to keep your gut familiarized with its ingredients. It's good stuff, but my first real experience with it was a definite turn-off.