Has anybody had success with fat burners?

Just curious & thought I'd ask here as well as reading reviews online & stuff...I'm a big fan of Jodie Marsh & follow her on Twitter, she's recently brought out a range of supplements/protein shakes & one of the more popular items according to Twitter is a fat burner called Semtex which people claim can make them lose a lot of weight in a short time. Now I know that diet & exercise are the way to go & that there are no miracle pills, but these & similar fat burners claim to give you a boost in energy, suppress appetite & boost your metabolism to help the process along so I'm just wondering if anybody has had success with anything like this?