iOS 13 is now available to download, and if you’re reading this there’s a good chance you’ve already installed it. But if you haven’t, I encourage you to wait. You’ll need to turn off auto-updates in order to keep the install from ...automatically updating, though. Barbara Krasnoff explains how to do that here.
You should wait because iOS 13.0 is buggy. Chaim Gartenberg has a review and it’s worth a read, but the headline has it right: iOS 13 review: dark mode, a new Photos app, and bugs.
In fact, Apple quietly pushed up the release date for iOS 13.1 and iPadOS to September 24th — it was originally slated for September 30th. That’s just four or five days from when you’re likely reading this, and well worth the wait. I’d actually recommend waiting longer than five days to make sure iOS 13.1 fixes the various bugs in 13.0.