Taste: Somewhere in between concentrated gatorade and melted popsicle. I tried the fruit punch flavor and while I didn't have any problems with the taste exactly, I did have trouble with the volume/taste combo. The packet is 4 ounces, which is a whole lot of melted popsicle/sugar syrup to take down. Even though I am a girl with a major sweet tooth, it was just too much for me and I only ended up taking a little over half before I headed out on my run.
Energy boost: I definitely noticed the effects during my run. I had that extra bounce in my step, which is really saying something given my current fitness situation. However, with 23 grams of sugar, I'm not sure this would be my fuel choice at the start of a 20 mile run. I do think that its the perfect choice before a speed/track workout, 5k PR attempt, or a short/mid-length tempo run. Maybe thats why they've picked Mr. Bolt as their poster boy!
Overall: Good! I never retched once while drinking it and I would definitely try it again, but I don't think its the solution to my marathon fueling troubles. I think its a good option to get a quick boost before a high energy/intensity workout.