I broke the back glass on my 15 Pro a few months ago, still covered by AppleCare+. I made an appointment at the biggest store in town, and they didn't have the part in stock when I got there. The Genius ordered the part and told me they'd have it in a few days. Nine days later, they finally got it. I made a new appointment, showed up, and they told me they had the part but didn't have a replacement phone in stock in case something went wrong during the repair. They offered to have me go to another store nearby, which had both the part and the replacement device, but I opted to just take the gamble (since back glass replacement seems like a low-risk repair).

The whole experience left me very disappointed with AppleCare+ and the Genius Bar in general.

Why the heck didn't they have the part in stock given that I made an appointment several days in advance? (You go through a little menu saying exactly which part is broken, rather than a free-form text field, so their systems _should_ have known that they'd need a replacement back glass in my color.) Why didn't they tell me before I hauled myself in for my appointment that they wouldn't have the part in stock? Why does it take 9 days to get replacements? Why didn't the first Genius tell me that other stores in town had the part in stock? Why didn't they have the backup device in stock or warn me in advance of my second appointment?

I worry that Apple has gotten complacent with service because they can get away with it.

I'm sorry you had that experience. That has not been my experience, but I am on the latest iPhone so I could see that an older model might have more trouble. Hope you have a better experience in the future, it's not acceptable that's for sure. I'll keep this in mind when recommending AppleCare+ in the future.