There are many films made that I look at and say to myself, "I could have written a better movie than that!" - this is by no means that kind of movie. Inception is a magnificently crafted film, one that shows the talent of the filmmakers is far superior to most mere mortals.
Conceptually the film is complex as it comes from a completely fabricated world - however the manner in which the complex subject matter is clearly articulated through the film, and the strict adherence to the logic and the rules established in the film make for an amazing story that has never been told quite like this before.
The film is incredibly well made. The structure of the film and the clarity of the story telling despite the complexity of the concept is a testament to that fact. In terms of the themes it uses of man's tenuous grasp on reality and its subjective nature are similar to the ones that made The Matrix so popular, and comparisons have been made by others between the two films. I would suggest the comparison is as such; remove all the hokey elements from The Matrix; (its dated use of technology and the cyberpunk fashion, the poor acting, and the reliance on "mysticism" as a substitute for a substantial narrative) and nuture all the interesting elements (the aforementioned metaphysical conundrum surrounding ones perception of reality, gravity defying action sequences, and mind bending alternate realities) and the end result is the masterpiece that is Inception. (ie: The Matrix without the crap, times a thousand).
The cast is classy, the acting and direction is sublime. The movie feels well structured in that it seems like there is not a redundant scene in the entire movie, everything is carefully in place for a specific reason, something that moves the story forward somehow, even if you don't realise it on the first viewing.
A movie best enjoyed with as little prior knowledge about it as possible - though with the volume of hype for it, it may be hard to do so. A must see movie if you enjoy watching movies.