First of all, the card, being a Dragon-Type, looks awesome. He does, of course, have a 2x weakness to Fairy-type Pokemon, as all Dragon-types will going forward. He does have an interesting Ability to consider: Bust In. When you play Dragonite EX from your hand onto your Bench, you may move any number of basic Energy attached to your Pokemon to this Pokemon. If you do, you switch him with your Active Pokemon. While that Ability is very strong, what does he then have the opportunity to attack with?
Dragonite EX only has one attack, Jet Sonic, and it requires two Grass Energy and one Lightning Energy to use. It deals 80 base damage, but you may discard an Energy card to deal 40 more damage. 120 damage for only 3 Energy at the cost of discarding one is fairly decent. However, the combination of Energy required greatly limits Dragonite EX's playability. Therefore, despite being one of the more sought-after EX cards to collect from this set, he isn't getting much love in the competitive TCG atmosphere.
This isn't to say that Grass and Lightning decks aren't playable - quite to the contrary. The problem is that there are simply EX cards available that are a bit stronger than this one at the moment when it comes to deck-building. However, his ability to literally "Bust In" and deal some quick damage strategically is a fairly powerful move. He just doesn't have a deck that he can truly benefit at the moment. This, of course, may change with future X&Y Expansions.
I hope that he does become more playable, as this will make collectors happy to see his value rise. For now, he's not very expensive, so he's a nice inexpensive addition to any Dragonite lovers' collection.