The reviews of Surrogates were largely negative, and I can see why, but they're mostly a matter of expectations calibration. (Minor spoilers ahead, but they really won't impact your appreciation of the movie, they're all things you'll see coming, particularly if you've seen the trailer which gives away the final scene.)
The premise of the movie is that everyone lives through robotic surrogates that look just like people, and which they remotely control from a "stim-chair" back in the safety of their home. This is a fascinating premise in a lot of ways. The many ways this would be used, the benefits and disadvantages, the impact on society, the whys and wherefores of how it could come to be this way (and why the inefficency, compared to a simulated world, makes perfect sense), are ripe for exploration.
That's where the movie falls down, though. Apart from a few throwaway lines and plot points, none of that is explored. We do have one person trying on a body of the opposite gender, and a few people using "enhanced" bodies, but by and large, everyone just looks like themselves, only better-looking and in better shape, and everyone can do the same things they would normally do, only with better endurance and less worry about injury.
A few issues of the threats implicit in this possibility are glossed over. There's a casually tossed-off line about how you can't just jump into someone else's surrogate because they have to be carefully matched to your nervous system -- and then this gets ignored pretty much from then on. The communications between surrogate and stim-chair aren't even encrypted, and all route through a single central switchboard that can tap into or override them at will -- we take more precautions than that with email. Even the central threat -- a weapon that scrambles a surrogate so thoroughly it also scrambles the human behind it -- is glossed over.
Ultimately what we have as fairly serviceable action/suspense movie that only takes its "hook" as far as it needs to to get you to notice it, and then ignores it thenceforth. There's good production values, lots of scenery for Bruce Willis to chew up, a smattering of good action, and enough plot to keep you working it out in your head -- not because you won't see the twists coming like a freight train at night in a cornfield, but because you will need to at least keep a scorecard.
The one place that they do dig up the premise is to make begging-the-question "arguments" about how this technology sucks the humanity out of humanity. They do this by simply presenting it as a fait accompli: a few people have used it to escape from things they should be facing, or find it's "not for them", and while lip service is paid to the good side (the virtual elimination of disease, death due to injury, and most prejudice based on bodies; vast reduction in crime; restoring full functionality to the disabled; and more), ultimately this is all deemed unimportant compared to a few people feeling less alive instead of more alive this way, and some blurry first-year-liberal-arts-major sentimentality.
Compare this movie to Strange Days and it will make you ache, because Strange Days does better as an action movie, and as a mystery, and as a character piece, and still manages to find time to give its similarly-scoped central premise a really thorough workout and exploration, finding both the good and bad uses. (It's hard to avoid the comparison when both movies feature a dreadlocked, black cult-of-personality character who is the de facto leader of an insurrection against the current order of society, too).
So in the end Surrogates is barely a tenth of the movie it could have been, if they'd really spent any thought on their premise, or given it a fairer, less dismissive analysis. But the movie it is, is okay for filling up a few idle hours when you're not looking for much. Expect that, instead of what the ads want you to think the movie is, and you'll be fine.