I haven't used them, but every time I see this question I find myself wondering why anyone would need them if they were already following a low carb plan?
From what I've seen, though, they generally don't work. Save the money that you would spend on starch blockers and get a nice steak and some fresh veggies instead.
I have a feeling that those starch blockers make a lot of claims that they can't deliver on. Really...if there were a magic pill that allowed folks to eat whatever they pleased and still lose weight that worked, wouldn't it be headline news across the nation?

You also might find this link interesting: http://www.quackwatch.org/01Quacker...s/blockers.html