Last May I bought my current Z Flip4. A few days ago a sensor at the hinge began to malfunction, causing the device to believe it was closed when it was actually open. I'm not sure it's entirely a hardware fault of the sensor as I see weird screen artifacts when I open or close it, though maybe it's a result of the sensor rapidly toggling the display. But regardless it has rendered the device unusable for some time after it has been unfolded.
Luckily, visionary I am, I bought the device warranty for $11 / mo, and even though I figured the cause of device destruction would have been from my own hand, this warranty covers everything short of intentional destruction of the device. This phone has two screens after all: a main screen and a cover display, and I wagered that I would have cracked at least one of them, but the reality is that I rarely drop this thing as it fits so snugly into my pocket when folded.
I have heard that another failure mode is that dust can get under the screen and can cause the screen to pop out after unfolding it.
Comparing Old and New
After activating the warranty I received exactly the same device roughly 3 days later. With both phones in hand, the first thing I immediately noticed is how prominent the crease is on the used one. The crease is easily detectable by touch alone and when held sideways in slanting light it is very clear where the screen folds. With the display on, however, I can detect no difference between the new and old as the crease is invisible to the eye in this case.
There is almost no perceptible crease in the new phone at the hinge, which is amazing considering the phone physically folds to half the size. The hinge is stiffer than my used Z Flip 4, however, and takes some effort to open with one hand.
Otherwise they're exactly the same phone. And I love the form factor in my hand. The camera is not amazing but taking pictures with the phone folded is really neat. The cover screen is great for checking notifications quickly too. Here's to another year!