QR Codes have been around for some time now. I myself do not use them that much, but I do see them everywhere. Last night I was designing the new Loftway postcards and I decided to include QR codes in it. Each listing has a QR code directing to the listing page where clients are able to see more info and pictures.
I also did some research to see if people really use them. It seems like its bigger in Europe than in the USA. One of biggest mistakes companies do is to have QR codes directing to sites no optimized for mobile users. Most QR codes are scanned with a cell phone and therefore this is very counterproductive.