Apple's massive overhaul to its iPhone and iPad operating system, iOS 7, is now available. If your eligible device is reasonably up to date already, you can just click Settings -> General -> Software Update to download it straight to your phone, but be careful! It's a major change from the iOS you know, so it pays to learn all about it first.
If you do nothing else, click "Learn More" when it tells you that iOS 7.0 is available (see screenshot). You'll see a lengthy list of stuff worth skimming before you commit.
Update - Wednesday, 5:45 p.m. ET: We've upgraded an iPhone 5 here, and it's been acting funny, occasionally powering down, and showing low or no battery. Hopefully with a full battery charge and a manual restart or two, things will work themselves out, but it's annoying for sure, so it pays to be cautious!
Others we've heard from on Twitter are experiencing congestion in the download, or a hang-up in the installation process. Most people may be doing fine, but this does not seem to be a completely hiccup-free process. Good luck, and feel free to let us know on Twitter at @wjrothman if you're having any troubles of your own.
Update - Thursday, 11 a.m. ET: We've now successfully updated two devices, an iPhone 5 and an iPad Mini, and both appear to be working smoothly. The iPhone 5 had weird battery issues, but since it's been fully charged, it has not given us any trouble.
Also, some of the long download wait times reported in Software Update — "19 hours," "35 hours," "48 hours" — appear to be wildly overcautious guesstimates. Most people who have seen those high wait times have been able to upgrade their devices within an hour or two, so don't give up.