This just opened in Australia today, so I went and saw it. Just got back about half an hour ago.
The end - Max leaving the island, saying goodbye to the wild things and returning to his mum - was lovely and poignant, with a strongly implied sense of leaving childhood, or at least early childhood, behind, which echoed beautifully with the opening of the film, which was also great and showed clearly without ever over-doing it how everything in Max's life is changing except himself. I thought these two bookends to the film were fabulous.
The problem was in the great big long middle of the film, basically everything on the island up to all the wild things saying goodbye to Max. This never really engaged me emotionally at all, much less to the extent that the parts described above did, and in fact I grew quite bored of it - which is not good in a film that's just over one-and-a-half hours long (very short by contemporary standards). My main problem with the film, though, was pretty much exactly what I feared it would be: there was no real sense that the wild things were actually wild. Sure, they engaged in the odd bit of consequence-free destruction and child-like play-fighting (and yes, I know there's a point being made about the wild things' behaviour, and Max's own behaviour, and how they're a reflection of his own childishness); but there was no sense of genuine danger in the film. Remember, it's based on a book which initially met with outrage from many parents, who thought children might actually find it terrifying. The wild things in the book really are wild and animal like and they crown Max as their king because he frightens them. In the film they're basically the cast of Friends in giant fur suits. Apart from occasionally referring to eating people, they're soft and cuddly and feel like the kind of people you might meet in an inner-city coffee shop talking about what's on their iPod.
Basically the film seemed to me like a real missed opportunity to make something genuinely strange and unsettling, which I think would have made the lovely bittersweet scenes at the end all the more powerful. Disappointing.
