I received a sample of cytonox with my recent order from bodybuilding.com. Although it is futile to rate a product based on 1 serving, I will just give a couple of quick thoughts.
1/3 of the packet is one serving...so I decided to take the whole thing

which was nearly 400 mg of caffeine. To my surprise, I did not get the instant rush that I do with my two favorite pre-workout supplements: vasocharge and shock therapy (both of which I take just a little over 1 serving).
The taste was similar to cell-tech fruit punch...which is not surprising since this product is made by muscle-tech. I am not a fan of anything flavored fruit punch...but this was pretty decent tasting.
I had to mix it up between every sip b/c of settling at the bottom.
I did get a great pump from the product. After the workout, my arms were so full of blood, that they measured 1" bigger than normal.
So, all-in-all, not a bad product based on my sample packet. However, I will be sticking with shock and vaso.