I saw Inside Man with a buddy of mine who figured out The Sixth Sense about ten minutes into it. He's good at figuring out twist endings and ruining movies for himself. Fortunately for him, Inside Man doesn't have a twist ending.
The thing about twist endings is that you're not supposed to see them coming. You think you're watching one movie, then suddenly you realize that you've been watching something completely different. When it's done well, you don't mind and you even get a thrill from it. When it's not, you've got two hours of eye-rolling ahead of you.
Mysteries don't count as twist endings. Everyone knows that there's a secret and that it's something we're all supposed to be figuring out. The mystery succeeds or fails on how well it conceals the solution while still playing fair with the audience. Inside Man succeeds by giving more than enough clues to its solution, but moving at so fast a pace that you don't have time to put them all together until the end when you're supposed to. It also keeps you good and distracted with great dialogue that's both funny and insightful.
The performances are also helpful in giving you something else to think about. They're all as excellent as you'd expect from Denzel Washington, Clive Own, Jodie Foster, Willem Dafoe, and Christopher Plummer. And they're better than you'd expect from a typical supporting cast.
And the music... I'm don't buy a lot of movie soundtracks, but I'll be getting this one. Mostly for the theme song "Chaiyya Chaiyya Bollywood Joint" by Sukhwinder Singh, Sapna Awasthi, and Panjabi MC.
I do have a couple of criticisms of the movie, but they're minor. The solution to the mystery is revealed to the audience before Denzel figures it out and the movie slows way down at the end as he puts it all together, but it's worth sticking with to get to his reaction when he figures it out.
My other minor criticism is with Jodie Foster's character, but not with the way she's written. On the contrary, she's one of the most interesting characters in the movie. She's unlikeable, but not completely so. For example, there's a scene where someone calls her the C-word and you can see brief shock on her face before she smiles and decides to take it as a compliment. We completely believe her when she tells Denzel later in the movie that her bite is much worse than her bark (there's never a moment that she's not being almost obnoxiously pleasant), but in that one, brief moment with the C-word, we also see that she's human. I'd never want to spend any time with her, but I liked the character a lot.
What makes her frustrating is that she's so intriguing, but her purpose in the story is purely to serve as a device through which we learn certain behind-the-scenes information. She doesn't impact the story in any real way. But, like the dialogue, she's an awful lot of fun to be misdirected by.