Alternate theory on the ending (spoilers, obviously)
All the twist endings around the time The Illusionist came out, and the incongruously happy and serene fairy tale ending here got me thinking.
I haven't seen this theory expressed elsewhere, so there are probably one or more good reasons why it's incorrect. But until enlightened, I will consider this added layer of brilliant psychological insight to be the obscure, pivotal masterstroke of The Illusionist, setting it a step above a lot of other movies.
Theory: Leopold did kill Sophie. The ambitious, exceptional Eisenheim was crushed by the state. The film's happy ending exists only in Uhl's mind as the bureaucrat's self-justifying rationalization, which allows the otherwise decent, intelligent Uhl to feel better about carrying out evil acts under orders from a tyrant.
According to this theory, Eisenheim didn't have a Super Happy Ending (S.H.E.) to look forward to after Sophie's supposedly faked death. And he wasn't delaying the S.H.E. and putting it at added risk to stick around and frame Leopold for a non-murder. His motivation for destroying Leopold was to seek justice/revenge, and not just a lark or political act. He was adamant about exposing the murderer of his beloved Sophie.
As partial evidence, look at Eisenheim's face in the scenes after Sophie's death. Does he seem to be up to one last elaborate trick on his way to indulging in his lifelong dream of running off with Sophie? To me, he looks like he's half-dead himself. This lies is stark contrast with the bright, sunshiny Norton of the last scene.
Instead, during the final scenes, Uhl, like the viewer, would very much like to think that the worst hadn't happened. Then, in a moment of revelation (and here, the director chooses shots which circle Uhl's head to designate the switch to his perspective), Uhl and we, begin to sense that this may be another twist ending. Maybe Eisenheim found a way to pull it off?
Uhl congratulates himself on his own powers of observation and memory (how reliable!), and his ability to pull together all the threads into one narrative, which just happens to be self-serving. He's got quite a smile on his face in that revelation scene, hasn't he? He's satisfied with himself despite the evils that he is at least partially responsible for during Leopold's reign.
The film's final illusion is Uhl's.
Plausible?