I'll agree that the careers in the movie felt more like school bullies than ruthless fighters trained to kill. Clove was the only one I thought really came close to the brutality of her counterpart in the novel. As they were skipping and giggling through the woods I couldn't help but roll my eyes a bit. I've liked Leven Rambin in other things in the past (Glimmer), but I was disappointed with her in the movie.
That said, from another angle, their portrayal was in some ways more chilling than what I had imagined in the books. The impression that especially Marvel and Glimmer gave, of this being a game with obstacles to be disposed of, it just seems like a gross exaggeration of how battle games are viewed today. How many generations are we truly away from considering people disposable in pursuit of our goals? Certainly some of our reality competition crazes promote that mindset to a lesser degree - the ones who win are often the ones who will step on and betray whoever they have to in order to get what they want.
Yes, it is an extreme extrapolation. But that's kind of the point, and certainly what Suzanne Collins was commenting on with her story. There's an interview with her included with one of the audio books (I honestly forget which one) where she talks about what she was trying to say and what she hoped young people would consider as a result of reading her books.