All the "magic pills" used to be based on ephedra. Then they discoverd that ephedra led to serious heart problems for many consumers, so ephedra based pills were banned. So the manufacturers turned to caffeine. Now, some doctors are discovering with caffeine based hydroxycut.
Taking these pills is stupid, IMO. Each pill has around 600 mg of caffeine. This is what boosts your metabolism! In other words, you're fidgeting around so much, you burn off some extra calories. The same thing would happen if you drank 7 cans of Red Bull all at once.
And at a dosage of 2 pills with every meal, that's like drinking 42 cans of Red Bull a day! Now, I used to drink 10 cups of coffee a day, and most people thought that was insane. How do you think your body reacts to 36 cups of coffee a day??
And, as Dave so rightly pointed out, are you going to do this the rest of your life? Would it be safe to do it the rest of your life? Pills like this do nothing more than lure you into the "diet" mentality. They are temporary fixes.