I would say C4 is one of the better pre-workouts I've tried....and I've tried just about everything. Everybody's different but for me it gives good clean energy. I don't notice any bouncing off the wall affect but I do notice I am stronger and can go longer during my workout. In fact, I usually have to force myself to stop or I can overtrain (hmm, is there such a thing? Lol).
The one thing I do notice is if I take it in the evening I have trouble sleeping hours later. Morale of the story: good clean energy and don't take within 4-6 hours of nighty-night time.