On the other hand, recently I am hearing more anecdata about students using QR codes in other contexts, so perhaps it's just a matter of motivation and/or accustomisation.
Besides which, QR codes are pretty ridiculously easy to create and slap on a poster - it's not like the time investment, say, Second Life required. Even so, you don't want to clutter up important real estate (and potentially look a bit try-hard) if no-one's actually going to use the code.
So how to track the usage of your QR codes? It's just about as easy: if you create the QR code through a site like bitly.com (there are probably others, this is just what I'm familiar with) then it'll keep count for you of how many people are following the code.
For example, a bitly URL http://bit.ly/107etxA gives you a QR code at https://bitly.com/107etxA.qrcode and a stats page at https://bitly.com/107etxA+. (The QR code and the original link will both take you to the target webpage and will both be tracked in the stats, but the "referrer" stats will tell you which visits came from a website and which came via the QR code.)
Best practice: If you are slapping these on a poster, spare a thought for those who don't have a smartphone and include a human-readable URL as well. You could use that bitly one, in which case you might want to customise it when you first create it so it's also human-memorable. :-)
Out of curiosity: Is anyone out there already using QR codes and has their own success stories (whether quantitative or qualitative)?