My notes on the upgrade from 14 to 15 I took during the announcement:

  * Twice as bright screen
  * Dynamic Island
  * Smaller bezel
  * Contoured edge
  * New better plastic back
  * Big camera improvements
   - 48MP main camera vs. 24MP
   - Faster focus
   - Much better telephoto
   - Improved portrait mode
     * Better color
     * Better low-light performance
     * No shutter lag
     * Turn on portrait mode after the fact
   - Smart HDR for better lighting
  * Live voicemail transcription
  * Longer battery life?
  * Satellite emergency / roadside assistance