I saw it on opening day and as plainly shown by my avatar, I absolutely loved it. HTTYD is absolutely my favorite movie of all time. It was very fun just to watch and the amount of detail in everything that was on screen was breathtaking.
The story was about as cliche as the story in a children's movie could be, but it was still a great movie, being helped by the characters and the dragons themselves. Overall, though, my favorite part about the movie was the main title dragon, Toothless. He was a great example of awesome animation, being part dragon and part stealth bomber.
I actually want to go back and see it again.