Last night, the Department of Defense (DOD) sent employees and contractors an email "strongly encouraging" them not to upgrade their iPhones to iOS 13, but rather to wait for iOS 13.1. Users in the Apple's Developer and Public Beta programs are already using 13.1, indicating that release is likely not far away. The email, which I reviewed (and which was not classified), explains that iOS 13 is expected to ship with known issues that will be addressed in the upcoming 13.1 update.
DOD Mobility strongly encourages you to NOT update, to avoid known Apple iOS 13 bugs. Apple is expected to release iOS 13.1 at the end of September 2019 to address bugs. DMUC users can expect follow-on messaging within the next two weeks with updated guidance.
DMUC refers to the DOD service that allows commercial devices like iPhones to access enterprise functions like Defense Department email. Granted, the Department of Defense network, in general, has some pretty important information stored on it, and it makes sense that it would be more than hyper-sensitive about the software installed on devices that connect to that network. Still, you have to at least ask yourself whether you should be upgrading your device or waiting for the next release.
Interestingly, the DOD doesn't say what specific issues it has with iOS 13, beyond an action item that says:
Do NOT update to iOS 13 and iPadOS until further notice due to known functional issues that may break enterprise services.
It's worth noting that iPadOS won't be available until the end of the month, but the fact that it is not prohibiting the update should give you some level of comfort that your iPhone isn't going to start recording your phone calls and sending them to Russia. Instead, it's more likely that the DOD is referring to the fact that some enterprise services may not be immediately compatible with the update, and that Apple appears to be holding back some features for iOS 13.1.
I reached out to the Public Affairs Office for the Defense Information Systems Agency for comment, but did not immediately receive a response.
If you're wondering whether or not you should update your phone today, I'm not aware of any major issues with iOS 13 after running the developer beta for a few months. There were bugs associated with connecting to Wi-Fi and even cellular towers, which are the type of thing you expect in a beta software release. It would be highly uncharacteristic of any software company to release a mobile operating system to the public that still had those problems.
I wrote previously about the best new features of iOS 13, but the privacy features alone--like the restriction on apps tracking your location, and the new Sign in with Apple are worth the download. That, and the increased speed benefits will make even devices as old as the iPhone 6S feel newer and faster.
There are a few features that are apparently being held back for iOS 13.1, like the ability to send an ETA of your arrival from Maps, the ability to create automations in Shortcuts, and some visual changes (like dynamic wallpapers). There was also reportedly a bug that allows users to bypass FaceID, however beta testers and developers have confirmed that the version of iOS 13 that is shipping today is stable and Apple likely already patched a flaw that severe.
If you're convinced that updating your device won't be the end of civilization as you know it, there actually is a really good reason to wait at least a few hours or even a day. While the update will likely be available around mid-day on the East Coast, you should probably just plan to wait until you get home from work. iOS downloads can be notoriously slow at launch due to the number of people trying to update at the same time.