Training Dragons brings back the story of conflict of misunderstood adversaries. Characters develop, some scenes will have you rolling in laughter, and the end shows that not all gain comes without some loss. An excellent movie all-around, the IMAX 3D really helps this movie shine over alternate versions.
Do you like eye candy? See the movie. Do you dislike movies that have a deus ex machina? Skip it. This one has such in the most literal sense. Are you capable of enjoying things despite flaws? See it. It's from a dream the guy had, fer cryin' out loud. If you demand thoroughly thoughtful tales, skip it
See it in 3D. It's not gimmicky 3D stuff, just excellent immersion.
Personally, I liked it. Most of the folks I knew liked it.
"But, Kit, why did you give it 4/5?" Somebody did something that has only been done a handful of times in recorded history (movie lore history). It should have been an epic event. Instead, it was an anticlimactic cut-to-black.