I finally saw this movie, my pre-conceptions--voiced earlier in the thread aside--I did enjoy the film overall. I am somewhat disappointed, I was expecting a touchstone type of SF movie, possibly even Oscar material and what I got was something slightly above average but not particularly notable.
The metaphors: Both for the immigration policies of countries on Earth, plus the control of the Wealth and governing amongst a small portion of the population were obviously thinly disguised. I tend to think most people agree things will continue this way and get worse, though statistics show the wealth is spreading over populations in many countries. I tend to doubt this thought experiment/cautionary tale is likely to happen, at least on the scale that it does in the movie.
The technology: I think it's possbile much of the audience may not realize a lot of the healing technology in the movie may well come to pass on some level, likely even before the time period in the movie. I don't have qualms with that. Though Elysium itself is pretty magnificent, the movie really fails to convey that most anything else fits into this future, it's a little too safe and pat to be believable. Humans are basically the same as they are now, but the "out of touch" rich are even more out of touch. Elysium may as well be Wonderland. Now to protect this place, a unique way of life..there are no defense batteries, orbital satellites or interceptors, even though the people on Earth posses shuttles. There is however, a psychologically disturbed cyborg with a missle launcher on the planet...yikes.
So what will happen on an overpopulated Earth when everyone is healed? Well more space stations of course. Colonies on the moon, and expansion. But in the meantime, yes there will be chaos. What a mess the ending leaves everyone in.
I found Damon adequate in the lead role. Foster's role was underwritten and performed.