They are decent as app shortcuts it seems. In the last two weeks I’ve done it twice as a replacement for typing in the name in the App Store of some targeted one-off app that is for a particular piece of hardware. In the first case it was some LED lights for my nephew. In the second case it was some light up hardware for a KPop concert I went to with my wife.

We were using them to "check in" during covid. They were mmmm... moderately useful I guess but of course the whole idea got mired in controversy

I absolutely hate it when there is a QR code with text like "Scan here for more Information" or similar - and then there is no link written or no information on how to get there without having to scan the code.

The best use I saw was on some small electronics thing I was looking at in a shop. One brand had QR codes on their boxes, which led to a full specification and the user manual -- more than could possibly have fitted on the box, especially as a European box can have 10+ languages.

Another is joining a Wifi network. I saw this at a couple of small hotels recently -- as well as giving the network name and password, there was a QR code. Scanning it prompted me something like "Do you want to join NiceViewHotel Wifi network? Yes/No" and was much quicker than typing in the key.