I know I'm really really late on this, but I just got finished watching it.
So, to sum it up, the ending was predictable. Anybody with a single shred of common sense saw it coming. HOWEVER, what I'm presented here with that ending, and how it plays into the story... well... I thought it was really great. Martin Scorsese has the type of visual and acting command as a director that most directors WISH they could have. The visual look of this film, the cinematography, the production design... is GORGEOUS. I mean, there are shots in the movie that literally looked like they could be hanging in a museum somewhere. And, some scenes just work with the kind of editing rhythm that most films of this type lack.
The problem with the ending is not the ending itself, it's all through the movie. The film keeps tipping it's hand by showing all these visual clues that pop in at around moments. It is a problem with a movie like this that most audience members don't just watch the movie... They watch it to guess the ending, to guess the twist. They try and figure it out, it makes them feel like they are smarter than the director. So, if you watch this at all, STOP thinking about the ending, just watch the movie. You'll like it better.
If the ending was slightly less predictable, then this would be a near-flawless film for me... HOWEVER, with what we have here, it's still a 9.0 out of 10.