With iOS 6, you can now do something simple, yet cool—set an alarm to wake you up with a song from your music library. To check out this fun new feature, just go to the built-in Clock app on your iOS device, and then click on the Alarm tab at the bottom of the screen, where you'll see a list of any alarms you've previously saved. From there, you can either touch the Edit button to change an existing alarm or tap the plus button to create a new one.
When you get to the Add/Edit Alarm screen, you'll be able to select the time you want the alarm to activate, obviously (wouldn't be much use without that!), but you'll also notice that you can add a repeat of the alarm, change what label pops up on your screen when it goes off, and select its sound.
I promise you that if I ever have to wake up as early as that alarm indicates, there won't be enough coffee in the world to contain my rage.
So choose Sound, and from the next screen, you can select an existing tone you've got or buy a new one if you're all funky like that. If you tap the other option, Pick a song, you'll be able to do just that from your existing music library.
When you're done configuring the alarm, just go back to the Add/Edit Alarm screen, click the blue Save button, and you're finished! And now the soothing sounds of Black Sabbath can wake you gently from your repose.
No offense, Apple, but this feature sure took you long enough.