It is a little thing but anyone playing a game like Dying Light knows how much of difference having wet shaders on objects during rain makes the game world so much better looking. They even made a mod for Skyrim that added bouncing rain drops on the ground.
I thought I saw puddles in trailer when it showed a character walking down a street in one of the settlements. But I don't know if they were static or dynamically added. Did anyone notice any evidence other than that of wet shaders?