Back in the day, iOS always showed On/Off Labels on toggles, making various Settings appear like a power switch. More recent versions of iOS have removed this indicator, opting instead for a more clean-looking design. For those who could use an additional visual cue besides the color green, or simply enjoy the old look, it's possible to restore these labels.
While Apple has yet to offer an official "Dark Mode" setting for low light environments, iOS 11 does offer "Smart Invert Colors" in the Accessibility settings, which basically turns white backgrounds to black and black text to white (and vice-versa) and dims bright colors. This makes viewing in low light situations easier on the eyes and less distracting to others around you. Unfortunately it is not very easy to get to in a hurry because it is buried in Settings -> General -> Accessibility -> Display Accommodations -> Invert Colors -> Smart Invert.
When it counts, missing an incoming phone call on the iPhone can be a problem. While the volume can be cranked up to the maximum, there are situations where vibration can help. There's another option built into iOS that's designed to offer visual alerts. Incoming calls or alerts can trigger the LED flash on the back of the device to blink.
Asking Siri questions verbally can be convenient, and Apple has designed its personal assistant to operate completely hands free with Hey Siri. This voice functionality takes on new importance with products such as the HomePod. There are situations, however where iPhone and iPad owners may want to access Siri without making any noise. In quiet areas where speaking out loud would be disruptive, Siri can be used silently with Type to Siri.
The iPhone X is longer than other non Plus-size iPhones by about .2 inches. On top of that, the Control and Notification centers are opened by dragging down from the top corners, which can make the task quite awkward, especially for those with smaller hands.