You need to think a bit to understand what is happening; I had to stop half way to review the storyline in my head; but once you do understand it, it is BRILLIANT. Even though I needed to think about it, once you understand it, its amazing.
I see others putting 1 star reviews because they didn't stop to go over the plot so far to connect the dots of the story/rewatching it it. I myself thought it was not a good movie because I couldn't understand the plot, and the time twisting, and the physics bending, and the how inversion worked part of it. when I took a midway pause however, to review the story and different perspectives of the characters, it was amazing in its difficultness to understand. Christopher Nolan is known for his mind bending concepts portrayed on the big screens, and this is no different.