Why are some events shown 2-3 times?

There's no change in camera vantage point but there are changes in story vantage point. If you see what I mean? I think they're important to the telling of the story and you can see how he went on to use the same idea in Memento?

Not really repetition. Keep you wondering "why has this happened?" until it's shown fully later on with right perspective.

It was a bit annoying in the beginning, but I got into it as the movie kept going. Have seen few other movies do this (not sure if I hate it or like it).