If you depend on hearing notification sounds for third-party apps and/or features that rely on the default notification sound built-into iOS, do NOT upgrade your iPhone to iOS 17! A stealth change Apple made to the sound of push notifications was to default it from the familiar Tri-tone to something called "Rebound". This sound is many times lower in volume than the old Tri-tone, and Apple in their infinite stupidity gives users no way to change this default sound, and people have been rightly screaming about it for the 9+ weeks it's been out. If you want to hear the difference, go to settings ---> Sounds & Haptics ---> Text Tone ---> Rebound for the new one, and then scroll down to Classic ---> Tri-tone to hear the old one you're most likely used to. If you're in an environment that has any fair amount of ambient white-noise level, like a grocery store or outside on a windy day, you won't hear the new sound if the phone is in your back pocket, and if you carry it in a purse or fanny pack, fuggheddabouddit.
I won't for the same reason that when I buy a new Honda and don't like the radio, I won't throw it away and buy a new Toyota because it has a better one.