There are many great things to discuss about this film, but today I was thinking about its structure, primarily the midpoint of the film.
It reminds me some of Close Encounters, in that there is a cascade of negative situational changes that readjust our awareness and hopes and fears.
In Inception that cascade climaxes with the realization that we literally cannot turn around, cannot go back, we cannot fail, there is no safety net, we don't wake up now if we die in the dream. New game. New stakes for the whole team.
And we get it in a way that Chris Nolan loves to deliver it--a surprise downfall realization about our "hero."
They must now get aggressive, go deeper, Mr. Charles, etc. Turning back is Limbo for who knows how long.
A great great film. Written and directed by Nolan.
Be well.