It's probably not indicative of everybody, but I was extremely successful doing the low-carb thing while ingesting lots of caffeine. Seems that Atkin's said no to caffeine, but we all have our little weaknesses. My wife discovered that aspartame would completely derail her.
I tried the south beach diet and lost 15 lbs (I found five of them though). I'm doing pretty good just calorie counting. It's not as fast, but I can live with it.