I think people know it exists. The problem is that it doesn't do anything remotely useful, except for the iPhone keyboard cursor thing.
> Siri (which everyone raves about but nobody uses for anything).
I use it all the time (at least once a day) to add a reminder, set a timer, set an alarm, check sports scores (I don't really follow sports, so this will probably end after the Warriors' run), call someone (I do this rarely enough that I'm incredibly slow trying to figure out the Phone/Contact apps), or do a Google search. I would love some basic improvements to Siri UI, like sending my Google search straight to google.com instead of reading my entire query back to me first.
> what the hell the volume button does in different contexts
I've never had a problem with this. Another commenter already covered it, but it's extremely predictable and fairly obvious.
> turn off buzzing and booping when I plug in a charger, and maybe some sort of wireless charging thing if the technology is where it needs to be yet
Charging cues have never bothered me in the slightest, but I see no reason not to have a setting for it. Wireless charging would be absolutely huge. It's probably my number one feature request. I'd probably pay for a brand new 6s if all they added was wireless charging. Heck, I don't even need it to be fast, just let me set my phone down at my office desk and bedside table and I'll be happy.
> stop showing album art on the lock screen (or make it optional)
Again, this is something I've never even thought about, but it's hard to argue against making it optional.
> more uniformity on how lock screen notifications are acknowledged and dismissed -- sometimes there's an 'x' in the swipe-over, sometimes actions, sometimes just pressing the notification does something
There's no reason not to fix this.