I purchased my iPhone 5 last October through Verizon. I rarely drop my iPhone and I always carry it in a protective case. My iPhone 5 practically looks brand new when you remove it from the case - no scratches, dents, dings, or other blemishes.
The other day, I noticed that the vibration (vibe) motor had stopped working. So, I took it to my local Apple store and they did something to repair it. I'm still not entirely clear what they did. They replaced the vibe motor but informed me that the problem wasn't the motor. They didn't replace the phone or the circuit board, so I retained all my data.
Then, today I noticed that the vibration had stopped working again! I was frustrated, but a few hours later I noticed that the vibration was working again, so I remained puzzled.
Nevertheless, I took my iPhone 5 to the Apple store because of a different problem: the sleep/wake button wasn't being too responsive. If you press the button on the left corner, it works fairly well. If you press it towards the right corner, it works less than 30% of the time. Failure of the sleep/wake button seems to be reported by other iPhone users. The Apple store replaced my iPhone with a new phone. Thank you Apple.
So, here's the bottom line: if your iPhone is still under warranty and you've noticed that the sleep/wake button isn't as responsive as it used to be, you may qualify for a replacement. Take it to the Apple store. Make an appointment online for the Genius Bar to reduce your wait time.