It was, in essence, everything I'd hoped for - to put it simply, good, enjoyable fun. If I had to make a criticism, it's that it didn't stay as close to the plot of The Secret of the Unicorn graphic novel (are we allowed to call the Tintin books graphic novels?) as I'd've liked...but then in all honesty, the plot of the original hardly makes for an exciting action adventure yarn. Rather, they've gone from something based on (but not 100% identical to) The Secret of the Unicorn into something based on (but not 100% identical to) The Crab with the Golden Claws (during which segment Tintin meets Captain Haddock for the first time, as is the case with the book of the same name), into something which (apart from a cameo by Bianca Castafiore) has no resemblance to any Tintin novel, but retains enough of the spirit of Tintin that only the most churlish of diehard fans could possibly complain. (I also felt that the chase through Bagghar owed more than a little to some James Bond chase sequences, and found myself wondering why Spielberg hasn't yet directed a Bond movie...)
The main protagonists - Tintin himself, Haddock, the Thompson Twins and Snowy - are all present and correct (of the regulars, only Professor Calculus is missing from this film; presumably he'll be in any future film, though), and come across much as one would expect (although the decision to depict Haddock with a Scottish accent was surprising), and many of the minor characters also make the leap from novel to film (including Tintin's housekeeper, Mrs Finch); although Sakharine, in the novel a collector of model ships who shows an interest in the model of the Unicorn which Tintin buys from the market, is here re-imagined as a descendant of Red Rackham and the main villain of the piece.
Technically, the motion capture and CGI used to produce the film is impressive. There is perhaps a case to be argued that the characters could have been made to look more like Hergé's illustrations; instead they fall between two stools - not quite cartoons, but not quite lifelike either, with individual characters veering towards either end of the spectrum - the Thompson twins are probably the closest to the novels' illustrations, Tintin and Sakharine closest to resembling actual people (although an early scene with Tintin posing for a caricaturist in the market has the final result being a dead ringer for Herge's original illustrations; a variety of supporting characters from other novels appear in the artist's gallery, a pleasant nod to fans of the books). The scenery tends towards the photo-realistic in all cases, and is uniformly excellent, in my opinion. The 3D is also well done, realistic but not too intrusive.
Overall, minor quibbles aside (and let's face it - if I want something that's totally faithful to the original plots with art directly imitating Hergé, I can always buy the DVDs of the '90s TV series), this film was, in my opinion, excellent, good fun, and pitched just right to be a real family film - perfect for all ages, and true to the spirit, if not 100% true to the letter, of Tintin. Here's hoping Spielberg and Jackson get to make more of these - if they do, I'll definitely be watching.