Inception is much more intelligent than an action movie needs to be and deserves all credit for that, but unlike what it claims it is hardly a movie about dreams. The entire reason dreams are fun and hard to capture is that they're organic near-nonsense from the mind of the dreamer, but in Inception the dreams are a gigantic world crafted by an architect, or just memory. It kinda looks like what would happen if you asked Escher to direct an action movie. There are tons of rules for the people that invaded the dreamer's mind and a dream within a dream within a dream.
It's well-spread that Nolan spent ten years on the screenplay, and that is what it feels like: Ten years of thoughts and construction being poured down on you. There are a lot of nice concepts put into Inception that are nice to find and it is a well-constructed movie. If Memento was a puzzle then Inception is a puzzle of a maze.
This is both a strength and a weakness: The movie seems to want you to take notes, see how much is in it and figure it out, rather than take a dive into the human mind. We do get some of that with Cobb's personal tragedy, but most characters get just enough personality to be distinguishable. (Ariadne in particular, since her main characteristic is that she is impolitely curious about Cobb.) This combined with the movies length made it a very tiring sit.
My judgement would be that Inception is an intelligent, rational action movie with a reasonably creative effect use and that it should be appreciated as such, but that you can skip it if that description doesn't sound appealing to you. It's not as renewing as some people might tell you, you can watch Paprika
to see similar themes handled better.