Lines are quoted from the official notes; buff/nerf tags are auto-classified from the numbers and can be wrong. Covers the 14 most recent Dota 2 patches PatchMeter has fetched.
▼nerfBase Movement Speed decreased from 290 to 285
✕removedRemoved Easy Breezy innate ability
▲buffTailwindPassively increases Windranger's max movement speed to 600
▲buffTailwindAttacks also grant Tailwind effect. Increases Tailwind duration to 3s and makes it undispellable
▼nerfWindrunMovement Speed Bonus decreased from 60% to 50%
▲buffWindrunCooldown decreased from 15/14/13/12s to 14/13/12/11s
✕removedWindrunNo longer upgraded with Aghanim's Scepter
⇄adjustTalentsLevel 25 Talent Windrun Cannot be Dispelled replaced with Powershot Executes Enemy Heroes Under 15% Max HP (Execute Threshold ranges from 10-15% Max HP Based on channel time and reduces with each unit the arrow comes through)