I really enjoyed seeing this over the weekend. The acting is very good all across the board, with only a few minor characters that are probably extraneous. Heath Ledger's performance is award-worthy.
The movie does not feel long (even at 2.5 hours) and the plot moves along quickly. Although somewhat violent, it is not out of place. It's dark and thrilling, and you really get into the characters quickly. I would not take my children to it (there were a lot in the theater) but the crowd seemed generally very happy at the end.