If you're going to have someone else fix your device, Apple is probably your best choice: the repair is inexpensive and won't void your warranty (in fact, Apple will extend your warranty from that day by 90 days). Plus, if you can get into an Apple store, you may be able to convince the Genius Bar to fix your phone for free (even if there's more than one hairline crack). Assuming you can make a timely Genius Bar appointment, it takes Apple about an one hour to replace your screen.
The main drawback to Apple's repair service is that if you're not near an Apple store, the company will take 3 to 5 days to fix your phone and send it back to you. Who wants to go almost a week without their iPhone?