I wore a button with a QR code of all my contact info to a conference last summer. About 12 people knew what a QR code was. Of those, approximately 2 of them were able to manage to download the appropriate software to their phone and scan it.
At GDC (and Emerald City ComiCon) last year, we started a viral campaign for a game update via posters that displayed a QR code. Not many people knew what QR codes were, but we only needed one person to know what a QR code is, scan it, post it to the forums, and kick that campaign off. Luckily one person who was at GDC did have this knowledge, and the kick-off happened in short order. Info on the campaign: http://wiki.guildwars.com/wiki/War_in_Kryta_Viral_Marketing Now our community knows what QR codes are, and if we use them again, they'll know that something interesting is up. :-)
I like that--you made a game out of it. Which makes sense, obviously, given the audience.
We could stand to use a lot more tools like that in my day job, I think. It's hard to teach people about new concepts and interaction models, but if you can make it useful/fun for them, they'll teach themselves.
Of course, I got started using the QR codes on my card as a selling point for skills that aren't common in journalism. Maybe I should be more careful: if we manage to make them more common, I'll have to find a new way to signify "hip, hireable news hacker." <grin>