Thousand Winds is a 5/6 flyer for 4UU. Those are fair stats for a 6 mana creature. It also has a morph cost of 5UU. The way Morph works is that you play it face-down as a 2/2 creature for 3 colorless mana. Then, you can pay its Morph cost to flip it face-up. Oftentimes, when it is flipped face-up, Morph cards have an effect. That is the case with Thousand Winds. When it is flipped face-up, you return all other tapped creatures to their owners' hands.
At the time, it was clear that this flyer would be an interesting card that should play well in the Arcanis the Omnipotent deck included in the Speed vs Cunning Duel Decks. But because of the large mana investment, it wouldn't see much play outside of Limited. It's also an underwhelming creature unless it's able to be flipped face-up. And as good as the effect is, it's extremely situational.
However, Thousand Winds does see some play in EDH. Commanders that have utilized the Morph creature include Animar, Soul of Elements, (who can cast it for much less with his effect) and Ixidor, Reality Sculptor (who is all about the Morph creatures). Unless you're building a Morph themed deck, however, Thousand Winds is a flavorful but not very efficient creature.