Finally got round to seeing this last night. Impressive film, densely plotted but not impossible to follow, full of enough ideas for a series of movies let alone one. It didn't feel like two and a half hours either as the strength of the plot and the layer-upon-layer structure meant you had to concentrate to keep up.
Apart from Cobb though, the characters were completely two-dimensional. You didn't actually learn anything about any of them in terms of background and motivation. Even Fischer was thinly sketched even though the film was set in his mind. The characters were there merely to serve the plot and showcase the ideas. It is interesting that none of Nolan's films even try to work on an emotional level. Fanboys might claim they find them emotional but Nolan clearly isn't pursuing or interested in that kind of audience reaction. He is focussed on expressing ideas & playing with audience expectations. The heart of the film is not the characters but the complexities of the plot and the world the film exists in. The tone reminded me a lot of The Prestige (which I preferred).
It was interesting that Nolan chose to injure Saito and not any of the others. He knew that the characters were so thinly-sketched that we wouldn't really care if any of them were in jeopardy. Note how there was no emotional focus on Saito dying. No scene with someone explaining what was happening to him. Nolan just wasn't interested. Saito was there purely to set the story in motion.
Ok, fanboys would say that the whole Cobb/wife/children angle was the emotional heart of the film. I personally didn't find it convincing and I think the key point is that, at the end, it doesn't really matter whether Cobb is in reality or limbo. It doesn't matter whether he was genuinely reunited with his children or not. The point about the ending is that it is a very clever trick, not an emotional resolution.
In a film without much humour, the ending is the biggest joke. But it's a joke played on the audience. Those last few seconRAB played brillliantly with the audience but it was just play, just a trick. On the way out, the general consensus in our group was that it was a very clever, entertaining film but it was all on the surface. If you could turn the film on its side as you could the dream world, you would find that the apparent depth didn't really exist at all.