You'd have to be pretty diluted to believe some of the manufacturers claims (like "500% greater weight loss") on many weight loss products.
That said, a good ECA stack WILL have a noticeable effect, whether its just increased energy, suppressed appetite, or a higher BMR. It won't make your gut instantly disappear, but added to a good exercise regimen, it'll give you that extra 5-10% advantage that may or may not be worth it to you.
I find that popping a Stacker before my workouts keeps me running harder for longer. Just keep yourself hydrated, and read the warnings. Too bad we have dumbfvcks like Steve Bechler to remind us exactly how stupid humans can be.