The premise is a killer and though the follow through doesn't quite do it justice, I enjoyed the movie overall. I had a similar feeling when I first watched Office Space though: I like Mike Judge as a writer, but as a filmmaker he's just barely adequate. I mean, he's a step above Kevin Smith in terms of staging and pacing, but his gags and his, dare I say it, comic vision deserve a little better.
Idiocracy is not as uneven as Office Space, but it generally feels more forced and lacks Office Space's laid back charm.
Still, I think Idiocracy compares favorably to most contemporary comedies, which says more about the low quality of most contemporary comedies than it does about Idiocracy.
My favorite Hollywood comedy of the last few years was The 40-Year Old Virgin, which was well-written and had a great cast, but the best thing I can say about the filmmaking is that it's professional and doesn't look like a half-assed job.
But none of the movies I've seen have compared to some TV comedies from the last few years: Arrested Development, anything with or having to do with Ricky Gervais, or Curb Your Enthusiasm.
Maybe I'm being a little too vague, but what I'd like to see more of are movie comedies that build gags through their moviemaking and not only through their stars' clowning. Not that there's anything wrong with the clowning, but I want the more elaborate gags of a movie like Used Cars or comedies get part of their humor from a unique visual style like Dick.