I'm glad to see near the end the mention of high-density displays. When designing icons, a 64@2x icon should be different than a 128@1x icon. Although the former is technically at 128, it is going to be displayed on a high-density display at a smaller size, and care should be taken to simplify embellishments and details that will just make it look too detailed when viewed.

For icon designers out there, I'm curious how many are already aware of this distinction and are designing icons accordingly?