I purchased some iTunes gift cards this afternoon and took advantage of my Mac’s FaceTime Camera to redeem the cards via iTunes 11. Here is a quick 20 second video of the process. For full instructions visit Apple’s support page at http://support.apple.com/kb/HT5556?viewlocale=en_US&locale=en_US.
The nice thing is that if you can’t miss type a number or letter. I redeemed three $10 cards. So far I this is the only new feature of iTunes 11 I like thus far.