I did my first 5K this morning and busted out my free sample of powerbar energy gels I got in the mail a few weeks ago.
I opened the package and was surprised. They were a little bigger than expected, and kind of tasted like gummy bears. My son (he's 3 1/2) had one and spit it out, he wasn't excited about them. I didn't really experience any extra energy, but running in 80+ degree weather in the sun isn't fun to begin with.
Overall, I would give them a 3 on a scale of 1-5. The taste wasn't bad, but I don't know what they actually gave me an energy boost.