It might seem a little odd, but the lock screen on your iPhone is a pretty feature rich aspect of the OS. It provides functionality that you want access to without having to access the phone proper, and has undergone some changes in iOS 7. So in the first of what I hope to be a short series of posts, here's a few tips and features you might have missed.
The first, and most well advertised new feature of the lock screen is access to Notification Centre and Control Centre. The little bars at the top and bottom of the lock screen are there to indicate that they are available, and morph into chevrons once Notification Centre or Control Centre are open. I won't go over the features available on these screens in depth, but most notably, where the lock screen used to only give you access to notifications received since the iPhone was locked you now have access to your entire set of notifications. Because of this, once Notification Centre has been viewed, the lock screen is cleared to reveal your wallpaper.
The home screen of course now also experiences the funky parallax effect.
The camera slider still exists in the lower right corner of the lock screen, and it's worth noting that sliding up from this corner will always pull up the camera, you need to be somewhere left of that icon to pull up Control Centre. This may be more awkward for right-handers with shorter thumbs, or may just take some getting used to.
The lock screen now displays a current timer, or the period left on the snooze for your alarm in place of the current date while active. If your iPhone is plugged in it will briefly display the charge level here before fading back to the date. When you're using a timer this is particularly useful; you can just tap the home button to see the current status where as previously your options were to either launch the app or ask Siri.
The final notable change is to media controls. Previously double-tapping the home button while viewing the lock screen brought up the media controls. Now they appear immediately on the lock screen above the album art. Pressing the home button once switches to the clock, and pressing it again returns you to the media controls. It's a subtle change but a nice one.