I use them, some are better than others, my workouts are long and heavy on the volume, and I find a good preworkout can really get you up for it, one to avoid is 'conqueror', it did have a good effect in training, but it also conquered my a$$hole...
One I really like is 'the curse', get it in apple flavor, even with one scoop out of the max 3 it really works well. and zero stomach problems.