Among Top 5 must-have mods. You need to use Content Manager, but that's probably the Top 1 must have mod, so IMO a no-brainer. This makes AC look so much better, wish Kunos would just get this as official content. You cannot make realistic skybox with just 1 set of clouds, like stock AC tries to do. This mod fixes the problem, and the visual boost it gives to AC is staggering.
Only "Complaint" I have is the low light conditions, that would need headlights IRL. Many modders do them, but for me it always felt pointless. It's like keeping a picture of your dream girl in your wallet, when she wouldn't go on date with you :D They look real, just as every weather preset in this mod, which makes the lack of working headlights painfully evident.