(There are lots of spoilers in here so don't read farther if you haven't seen the film and want to.)
My initial reaction was that it was surprisingly violent. The opening scenes of torture in the police station, and the way the little kids are so horribly abused in the slums, were pretty grim. But as one friend pointed out, they were actually fairly sanitized compared to the reality.
I think it bothered me because I went in expecting a piece of fluff, a feel-good fairy tale. Instead it starts off with all this grimness, and I began to think that perhaps there would be some more to the film. But in the end, it did turn out to be a fairy tale, and one which negated all the violence of the opening. Sure, he's tortured by the cops, but instead of beating a confession out of him and probably crippling him for life, all of a sudden they're listening sympathetically to his story and they send him back on the show to win his 20 million rupees.
They showed enough misery and poverty to make the audience feel like they were seeing The Real Thing, but then it's wrapped up with a fairy-tale ending so you can leave the theater feeling good and having forgotten all the misery because none of it really matters in the end. The slums are gone and replaced with high-rises, the bad brother dies heroically, the hero gets the girl, wins the money, and suffers no lasting effects from all the horrible stuff earlier, and neither does the girl -- even the face slashing results in a nice neat scar that the camera can linger lovingly on, rather than permanent disfigurement.
So, I feel like it's not a very honest film in the end, not even internally honest. There were a few interesting things to read about it over the past few days as well: A column about the area in Mumbai depicted in the film, which has some disturbing "slums-are-actually-wonderful" stuff in it but is worth reading. And a piece about casting the film which says Boyle ended up using real slum kids to play the children and had to rewrite the film in Hindi since they did not speak English.
I picked up a copy of the novel and I'll be interested to see how it differs.