My wife actually loved this movie and thought it was great. And I think it gave a great feel for the time.
Personally, I felt like it just missed. The story seemed to drag in some places. There were times I didn't care about the characters or what they were doing. There were a bunch of story lines that were hinted at but never developed.
Depp did an amazing job. I didn't particularly care for Bale's attempt at a southern accent; it sounded forced to me but I'm from Texas and Purvis was from South Carolina, iirc, and we have very different accents so I'll give him a pass.