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

And then all that "definitely going to be used for contact tracing only" data got shared around with the police.

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.