I admit that I'm really not a huge supporter of the Dreamworks movies. They make a good one every now and then, but most of their stuff is garbage in comparison to Pixar.
However this is actually based on a series of children's novels rather than a random new idea. So there's a little bit of a good foundation from the start.
I really liked the story and characters, and the whole Viking theme. Despite the slightly-weird looking faces Dreamworks always makes.
The movie starts out rocking, and escalates higher and higher just like it's hero Hiccup and his dragon Toothless. It really is the best movie the studio has ever put out, and rivals even Pixar's finest films. Do not miss a chance to watch this masterpiece.