I wouldn't do it. 20% APR and you'll end up paying the price of a MBP at the end.
X2...
If you do put it on a credit card, at least make sure your going to get something good in return like Kash and myself did. USAA offered me double manufactures warranty on anything i purchased with my card. I had intended on paying cash for my MBP, so i put it on the card, with the extra doubled warranty and payed it off with the cash i was originally going to pay for it with anyways.
I called them and asked for the details on the doubled warranty...basically, if anything happens to it as a defect after the first year of apple care, they will pay to get it fixed...or buy me a new one.
But then, i have home owners insurance through them too with the added computer and electronics coverage...ANYTHING happens to it...i spill beer on the keyboard, i drop it, get ****** off and smash it...whatever, they will replace it no questions asked as long as i can show proof that i actually bought and owned it(receipts, credit card statements, etc).