I was pretty disappointed when I first watched it. The cast was amazing, it was Nolan, it was scifi, it apparently had a very deep story, I was super hyped.
But the film felt too mechanical. I don't mean that in an intricate mindbending kind of way, sadly, but that the characters were robots, dishing out exposition and following plot points, intermixed with lots of obligatory shooting where nobody gets hurt. And the story itself wasn't overly complex either, just we need to go deeper.
It had a great premise/plot with a boring execution. It came out in the same year as a film from my other favorite director, Black Swan. Which had a boring premise/plot, but a great execution. I preferred the latter.
On a second viewing I appreciated Inception quite a bit better. Nothing mindblowing, but a good yarn with great sfx. Though I might have looked at my phone during some of the shootouts.