I'll start off with a couple.
I was seriously put off by Hollywood-style cliches (and/or what I would call "modular"script elements), inconsistent internal logic, and the way one was expected to swallow the myriad of questions revolving around how can you get in someone's dream without any explanation - worse, with the characters joking about everything as if it's so common it has it's own techie lingo.
I found myself wincing so many times while actually watching the movie. But I found myself thinking about it as the memory of actual actors' lines faded.
The movie wove together themes that so much more could have been done with: The necessarily limiting aspect of being an observer (that all information about the outside world comes to us through sense organs, which information is the only evidene that the sense organs exist in the first place) and related themes surrounding various states of consciousness, etc.
I felt they forced such themes into a Hollywood action mold. It could have been a much more intelligent, brooding film...far, far richer.
Even on its own terms, they could have explored the themes more closely. Did he actually wake up? Well, probably not - he 'returned home' on the same sunny day as shown throughout the movie, his kids were wearing exactly the same clothes, his kids were in the exact physical position they were left in, and of course...they show the top start to waver and fall, but then right before credits panned back to show it spinning perfectly again.
Ok, so if he didn't wake up, is it that he got lost in the furthest depths of consciousness but the mission was real? Or was the mission a dream along with everyone he dreamed about? Did he kill his wife and send himself under to escape? Or was his wife real, correct to jump out the window, and were the other characters therefore some sort of rescue team for him? So on and so on.
To me, it's not even clear the writers intended to provoke a specific set of questions. It's more like they designed it so pepole would keep engaging the themes invoked, but not sufficiently explored, by the movie.
It feels like a shame to me that they could have done so much more, absent the cliches, etc.
I would have preferered a movie probing the theme of someone slowly losing their mind as they experiment with the first developed technology of this nature. Is it working - am I in your dream/am I in yours, am I dreaming this? Basically, once you push the button, doesn't it become metaphysically impossible to "know" that you are awake again? After all, the movie postulated forced dream states that are far more detailed than actual dreams, where characters walk around with the same mental capacity as if they were fully awake.
(For philosophers who've looked into problems of personal identity, this would be sort of like a "dream" version of the "zombie problem")
I dunno, but then again, I'm no screenwriter.
All I can say is that it's almost always a bad idea to watch a movie based on a work you truly love.
When I was too young to read at a high level, my father read LOTR to me over the course of a year or more. A bit most nights. Since then, I've re-read it about once every 3 years. It is not a story about magic, rings, or elves.
It is a story about the only things that can raise a human being above animals. Duty, hono, selflessness, sacrifice. Doing what must be done only because it must be done. Mice who tread where giants dare not.
The movie infuriated me endlessly. I felt each was worse than the last. What killed me was that it seemed as if the writer had deconstructed LOTR, turning it into one very big outline with 6 levels of indentation. The writer left the most major elements, levels 1-2, in place. He then erased levels 3-6 and rewrote the story's details.
For example, the entire journey from Hobbiton to Bree is almost completely rewritten. Here's what killed me: FOR NO PURPOSE. The movie spent a long time showing the screenwriters version of the journey. It would have taken no more or less to just show what Tolkien wrote. The writer changed the story without saving time or improving on what was there.
Of course, the movie also Hollywoodified various elements of the story and generally dumbed it down. That is, the movie tried to make LOTR a story about magic and elves, when those were just the backdrop for a story about human nature.
Finally, the movie lost what all movies based on books lose: The language. Here, it is a travesty that no LOTR movie could avoid.
At this point when I reread the story, it's mainly for the richness of the language. The way each sentence, paragraph, and chapter is structured around the particular thoughts expressed. As a writer, Tolkien is up there with Hemmingway, Steinbeck, Fitzgerald.
And of course, his ability to describe abstract sensations can be breathtaking:
"And all the host laughed and wept, and in the midst of their merriment and tears the clear voice of the minstrel rose like silver and gold, and all men were hushed. And he sang to them, now in the Elven-tongue, now in the speech of the West, until their hearts, wounded with sweet words, overflowed, and their joy was like swords, and they passed in thought out to regions where pain and delight flow together and tears are the very wine of blessedness."