A note on some of the new features:
Double Tap can be found under Settings > Extras > Double Tap. It's not very sensitive by default, but you can adjust it.
The screen is supposed to turn on when you pick it up (makes Iris easier to use and also eliminates the need for Glance screen) and turns off (locks for security) when you set it down. It's not very sensitive so you might not notice it at all.
Fingerprint reader is always on when the device is locked. If you press the sensor when the screen is off, it will unlock immediately, no lock screen.
HP Display Tools will auto-launch when you connect to an external display. The app will black out the screen and display the time (almost like glance screen) after the time you set, and will remain unlocked until the set time. It's intended to be used with Continuum and the Desk Dock, but you can launch it anytime, and/or turn off the auto-launch behavior.
You can turn off Navigation Bar vibration in Settings > Personalize > Navigation Bar. You can also enable double tap to turn off here.
HP 12C Calculator is designed to mimic HP's physical calculator. The full calculator is only visible in landscape orientation. The Menu button in the bottom left has settings and help.
Charging LED will be red when charging, green when fully charged. Flashing red when battery is below 10%. Cannot be adjusted or disabled, although it's not too bright.