re: What are the benefits of 0% APR?

You still have to pay the minimum monthly payment every month (for most cards this is 2-3% of the balance), but you don't have to pay the full balance due. For example, say you charge $1000 this month at the local strip club. Your statement will arrive in the mail showing a balance of $1000 with a minimum payment somewhere around $25. Instead of paying the full $1000 you can pay $25 to the card and use the $975 difference to pay down student loan debt. Normally this would be a very bad thing to do with a high interest rate, but at 0% APR it is actually a good deal financially.

But if you don't even pay the minimum then you are in big trouble. Most issuers will not report you as delinquent (which hugely dings your score) until you are 30 days late, but if you are even one day late they won't report you (i.e. there's no score impact at all) but will usually revoke the 0% APR term and start charging you the full purchase rate. Obviously don't do this - pay at least the minimum a few days ahead of time just to be sure.

Regarding your credit score, most scoring models will ding you slightly once you have a higher balance than 50% of your total available credit, another one after 80% or thereabouts, that sort of thing. But the hits on your score are not large and not permanent either. When you pay it back enough to bring the number back down again (which you will right???) you get the points back. I personally wouldn't worry about it.

So if you are diligent about making sure the minimums are met every month and the full balance is taken care of before the teaser period expires, this will save you some money. For only $150 or so it may not be worth your while though.