> Physics interpolation in 3D

This is huge. Initially, Godot didn't support any interpolation, which meant you either ignore fps altogether (and your game literally plays slower, and therefore differently, if the game slows down from 60 to 30 fps), or you move physics code to the _physics_process() and suffer from stutter/jitter because the physics code and the rendering code slowly drift out of sync. Amazing!

EDIT: I forgot to mention the _third_ possiblity, which is that you write a bunch of custom code in GDScript or C++ which attempts to do the interpolation.