I have taken it. Alot of people equate it with legal speed, however--since I have actually DONE speed (back in my highschool years) I can tell you its not. Theres no skin crawling, no heart racing for me.
If you do it right, it can be a good jumping off point. What I did was take it for 6 weeks, stop for three and then do 6 more weeks. That seems to be plenty. As far as side effects heres what I had:
Increased thirst. (Not too bad, since you drink lots of extra water--which, incidentally, is good for weight loss)
Difficulty sleeping (not that big of a deal- just take unisom(which is basically benedryl)
Constipation. Take fiber, and have fiber one bars for your snack. Solves this problem.
If your bloodpressure is an issue, don't take this pill. You will get some nasty headaches- according to my sister. I didn't get a burst of energy from the pill. I loved the appetite suppressant though. Its wonderful to just fight the mental battle of eating less for a while, instead of having to deal with the physical cravings.
But its no miracle pill thats for sure...