Back when I was in college and didn't know what the hell I was doing, I had success with them, but this was when they contained ephedra. I know several ppl that have taken the newer formulas and none of them have had any appreciable success outside of that gained from massive caffeine spikes (which have way bigger drawbacks IMO). Regardless, what little success I have seen has been in the accompanyment of a strict diet, which really begs the question...
*shrug* I don't recommend them.
"Use what talents you possess: the woods would be very silent if no birds sang there except those that sang best." —Henry Van Dyke