The interface for QR App can be a little confusing; in scan mode, what looks like the standard camera app shows up, making it seem as though you have to press the shutter button then the Use button. However, this isn’t the case — if the app detects a QR code anywhere in its view, it’ll automatically take the photo and read the barcode. I did have some trouble getting it to recognize codes sometimes, though.
Another annoyance I had with QR App was that the app will automatically open Safari or the Phone app without prompt f the code contains a URL or a phone number. Sometimes I like to be able to grab the information, but use it later on. The app does save a history of the codes you read, but I just don’t like the way it switches apps without asking permission first.