0% Balance Transfers a good idea?

I've made some pretty dumb financial mistakes in the past, and am now working on paying off my credit cards. I've paid one off but still have $7,400 on another credit card at 20.99% APR! I know, stupid, right?! The credit card I just paid off is offering me 0% APR until Jan. 2012. After that, the interest goes up to 19.15%, even lower than my current interest! They charge 4% for balance transfers. Given my financial situation, I won't be able to pay the debt off entirely for about 2 years (I'm currently in grad school, so extra money is scarce). Also, I've asked customer service, and they said they do not back-charge interest if the balance is not paid off by Jan 2012, although I'm weary about trusting a credit card company service rep. Is a balance transfer a good idea? It seems like a really good idea to me, but given that I've been pretty financially stupid in the past. Thanks for the help!