Just got back from seeing it. IN 3D!!! (There was three 3D showings and one 2D showing. The 2D was much later and we didn't want to miss Doctor Who, did we?)
The characterizations were spot on for every character but Mr. Saccharine, who was wholly reinvented for the film. The plot was action-filled and contained some scenes not from the original comics, but I could justify why they felt the need to change it up: if you want the same, exact story from the comics, read the comics, or see the animated TV show.
Some people have criticized it for being too fast paced and not being able to connect emotionally to the characters. The thing is, Tintin lives in the moment, while I thought we got enough time to understand Haddock's character. Haddock's a drunk loser and it's Tintin who helps him get back on his feet.
And Snowy is awesome.