I have learned after much pain they can be an effective tool to swap around zero interest and leverage your time. Mostly of the 15 I use 14 are zero balance. This is key, never pay interest. That being said I too detest the current system, why " as soon as I charge 6k on my amex it hits my credit in a 2 days or less, if i pay it off it takes 30 days to hit my credit. Credit ratings agencies are a scam......