My grandfather always told me, "You can't rob from Peter to pay Paul." Normally, this is true, but I think using student loan money to pay off credit debt is not a bad idea.
First off, you're not talking about increasing your debt, but rather decreasing the interest rate you will pay on your debt. It doesn't take a financial wizard to realize that makes sense.
Secondly, you are delaying paying on this debt for another 7 to 10 years. Sure, interest will accrue, but as a student you don't have much income, so this is a critical period in which to minimize your monthly costs. Pushing your payment out makes sense at this point, but realize that you will have to pay it eventually. However, that monthly bill will have a lot less sting when you are making a great deal more money to pay it with at the time.
Thirdly, even though interest is accumulating, not only is it at a lower rate (hopefully) but the govornment will even subsidize a portion of it for you. I'm sure your credit card lender will not offer to do that on the $20k you owe them.
Fourthly, there is always the chance that a future employeer may be willing to pay back a portion of your student loans. May not happen, but it isn't unheard of. There is also loan forgiveness if you work in certain areas.
Lots of people believe that student loans are some sort of sacred "gift" that must only be used on tuition, books, school supplies, and things that are intrinsic to an education. That's too narrow-minded a view. Yeah, things can get messy real fast if you borrow too much and try to live like a big shot while in school. But by using student loan debt to replace consumer debt you are effectively lowering the amount of overall debt you have because of the lower interest and government subsidization of the debt.
I guess I would say go for it.