The film does come up with a lot of inventive ideas connected to the concept. Many of these are similar to present day Internet issues - for instance, you never really know who you are speaking to online; identity theft becomes possible; your online actions can be monitored - and shut down - by any number of government or commercial organizations; a range of issues around cybersex which for some might be a pale imitation of the real thing while for others it is better, or the only option. Issues of identity are critical to the plot and come up over and over again in different ways.
I enjoyed these and the many other ideas that are thrown out but I was disappointed they weren't taken further - in particular the ability to take over different surrogates, jumping from body to body, could easily be developed further for both action and dramatic sequences, and I think they've missed a trick here. The action sequences focus mainly on the fact that the surrogates are stronger so Radha Mitchell can leap around the tops of buses. Also despite the parallels, there's no sense that the film is actually trying to say anything deep about either identity or cyberspace.
I didn't really buy a few aspects of the scenario. Having just one corporation producing Surrogates, for example, or the idea of a weapon that could kill the operator as well as the surrogate - at the end of a day, if you shoot down a RC aircraft nothing happens to the controller! Thinking about it, I suppose it's vaguely plausible that there could be some kind of feedback loop that does something to the operator's blood pressure, with Scanners-type consequences.
Apart from the under-used but clever ideas, I found myself enjoying all the nods to other sci-fi films but wondering which of these were deliberate tributes, which were just lazy scriptwriting, either cliche or plagiarism, and which were coincidental. There were scenes that reminded me of I Robot, The Stepford Wives, Terminator and Independence Day, plus a moment in the ending which echoes Logan's Run and rightly so, it's a nice touch. I liked Rosamund Pike's character as by the end of the film you actually understand why she has come to view Surrogacy as such an attractive option. It's also fun seeing all the cast in both their ridiculously perfect Surrogate form and in their malnourished "meatbag" form, the result of spending all your time living through a Surrogate.