As I wrote in a post at Search Engine Land, we don't know yet whether QR codes are here to stay or whether they’re an interesting experiment on the way to something else, such as NFC-based marketing. But in the near term at least they appear to be gaining and increasingly used by publishers and marketers.
Comscore has come out with some interesting new data on usage patterns. Demographically the heaviest users of QR code scanning are 18-34 year old males who make more than 100,000 per year. Most scanning is done in the home (newspapers, magazines) or in retail or grocery stores.
Several years ago I wrote a white paper about the virtues of SMS based marketing that argued SMS was a highly versatile tool that could be utilized in many ways: on traditional ads, in digital ads, on product packaging and so on. I also argued at the time that consumer response to SMS calls to action also provided compelling analytics for traditional media.
That's exactly the way that QR codes are now positioned. Accordingly they'll probably replace SMS in some contexts as a mobile marketing tool -- if QR codes survive. But QR codes don't really do CRM loyalty marketing as well as SMS.