A friend of mine is unable to consistently scan QR codes with her 3G iPhone. A code that I can easily scan with the 3GS may not be recognized by her phone. Is the 3G just not as reliable at this? We're both using the Red Laser app.
The iPhone 3G's camera is 2.0 MP while the iPhone 3GS has a 3.2 MP camera... that extra 1.2 MP makes a whole difference in details. Those details are key in a QR code scan.
Also, the 3GS and 4 have autofocus, whereas the 3G does not. Therefore, the 3G is not able to clearly make things out that are really close, i.e., QR codes.