i can't find myself using QR codes on a regular basis although i am really exposed to them on a regular basis (business cards, ads,...) 
The reason? i think it is too painful to get them scanned. It requires a reflex we don't naturally have to open a special app to read them
QR code reading should be a native feature of smartphone. And they should be accessible in 1 or 2 click max so users are enticed to read them.
There is a killer app in every smartphone for this> the camera app. If it was able to read QR codes that would be great
And since is most new phones the camera is accessible in 1 click that would be awesome (in iOS5 it will be avail from the lock screen)
Until then, i doubt this can become a natural reflex for all of us
