The quest to fly at epic speed is long and complex. Revered reputation grinding, Heroic instance running, escort quests, exploding foliage and much more await the intrepid druid. Oh, and they have to pay the 5000g riding skill upgrade before they can even start the quest.
When they finish, druids not only get the Swift Flight Form ability, but also a relic that works for any druid spec: Idol of the Raven Goddess - Increases the healing granted by the Tree of Life form aura by 20, adds 9 critical strike rating to the Leader of the Pack aura, and adds 9 spell critical strike rating to the Moonkin form aura.
An excellent walkthrough, Wiki style, can be found here at the Servants of Seagis guild site.
EDIT: Another reward received in the quest chain: Charm of Swift Flight, Trinket, Equip: Increases speed in Flight Form and Swift Flight Form by 10%. Thanks to Felixia from the Uldum Server for the heads up!