Dark Mode
Dark Mode may have been one of the most anticipated new features coming to iOS 13, and for good reason. The new mode makes certain user interface elements and apps look much cleaner and easier to read than before. This was especially true when it came to text-heavy apps like Mail and Messages, since the white text pops sharply against the black background, making it look even crisper than in standard mode. I especially liked how the blue bubbles that surround iMessages looked in Dark Mode compared to the standard mode.
Bluetooth and Wi-Fi options in the Control Center
For years, you've had to navigate to your iPhone's Settings menu to search for different Wi-Fi networks or nearby Bluetooth accessories. Thankfully, that will no longer be the case in iOS 13.
From the Control Center, just press and hold on the section that contains controls for airplane mode, cellular, Wi-Fi, and Bluetooth, to launch these settings in a standalone window. Then, press and hold on the Wi-Fi icon to see nearby Wi-Fi networks without having to launch the settings menu. You can perform the same action on the Bluetooth icon to connect to nearby accessories quickly.
It's a small but useful addition to the iPhone that makes connecting to networks and accessories much more convenient.
A more natural Siri
In iOS 13, Siri's voice will be entirely generated by software, and it sounds much more natural. This might not matter too much if you typically just ask Siri about the weather and traffic. But I found it to be really helpful when asking Siri to read my text messages out loud. Siri's inflections are much more natural, and she consistently interpreted common abbreviations like laughing out loud (LOL) and rolling on floor laughing (ROFL) whereas the Siri in iOS 12 would sometimes just read those shortcuts as a word.
Faster Face ID
The 30% speed boost for Face ID in iOS 13 may be slight, but it's certainly noticeable, making the feature feel smoother and more useful. I found that Face ID on my iPhone XR running iOS 13 generally worked in between 0.74 to 1.02 seconds when I timed it, whereas my iPhone XS Max running iOS 12 would do so in anywhere between 1 second and 1.1 seconds. It's a small boost, but one that comes in handy given the number of times I unlock my phone on a daily basis.