Well, the Player's Handbook 2 is here, and it adds the best flier in 4th Edition yet: The Scion of Arkhosia. This class is a Dragonborn paragon path, that allows your Dragonborn to grow wings!
At 12th level, the paragon path gains an At Will Utility Power that allows you to to fly your speed as a movement action. You do have to land at the end of your turn, but it is a great tactical option.
At 16th level, you actually gain overland flight at a speed of 12. Sustained flight at last!