I know a number of people who have been disappointed with the service at the Apple Store for one reason or another, but this continues to be the complete opposite of my experience. For the last few weeks the power/sleep button on my iPhone 5 has been developing a fault; becoming unresponsive unless you manage to push it with the right finesse. With only about a month left on the warranty I decided to take it in now, rather than wait for it to fail completely.
I managed to book a convenient Genius Bar appointment via the Apple Store app, which was not a flawless experience. It took a few tries to register the appointment - as other appointments were filling up each time I attempted to book I presume this was an issue with the volume of traffic. Still, it was mildly frustrating but I was successful after a few attempts. The Apple Store was heaving with people, and I had to wait a while to get checked in and then wait a while longer to get seen. Maybe 15 minutes in all - not too bad.
The Blue Shirt took a couple of pushes at the button to confirm the fault, and informed me that a replacement was in order and importantly in stock. There's something nice about getting a replacement - not quite as nice as the free upgrade I got when my MacBook had to be replaced - but satisfying all the same. He recorded the condition of my phone as 'Great!' and once it was erased handed me my replacement. The whole exchange took under 5 minutes.