Nanites have gone mainstream. We've been reading about them for decades. They've made appearances in Star Trek TNG and Stargate SG-1, but when they are central to a Vin Diesel movie, it's fair to say that they've become firmly part of the public's 'standard' sci-fi elements like warp drive and teleportation.
I had pretty high hopes for this movie, but it is yet another picture that is in that vast grey area between being great and sucking. The production values were very strong. The nanite visuals were something new, like high-tech bullet time. We get a ton of slow-motion shots of Vin's character being taken to pieces only to have his swarming nanites rebuild him nearly instantaneously.
As fun as that sounds, it became a problem because every fight's choreography was dumbed down to have Diesel stand in front of entire magazines of ammo to get those visuals. He's supposed to be this special-forces operator, but forgot about body armor, tactics, etc. It's just one fight after another of him letting guys empty their guns into him before he destroys them. No doubt that lack of concern for his own body is meant as demonstrative of Diesel's character's suicidal determination, but it quickly becomes asinine.
Then there's the story, the absence of it, that is. Diesel's character (Ray Garrison) has no real motivation. He learns early on that what's been driving him were false memories designed to pull optimal performances out of him. After that bubble is burst he becomes just another raging, muscle-bound idiot. I didn't care if he succeeded or not. So tension and suspense? Not so much.
The big-picture plot is likewise weak. There's almost nothing at stake. Guy Pierce is a strong performer as the antagonist, but he has precious little to work with on the page.
Lamorne Morris steals the show as Wilfred Wiggins in the few times we see him.
I'd like to say that Eiza González is more than eye candy, but she's not; she does an admirable job with her martial arts bits, but in the end her character is a cutout who exists to be a hot, empathetic chick who cares for the studly main character, and looks amazing doing it. In keeping with the overall machismo of this movie, women have little agency in this film; they exist only as objects of men's desires. I'm not so offended by it as disappointed. González is talented enough to do a lot more, they just didn't write her a role worth a damn.
Another problem with this movie is the Groundhog Day effect. Vin's character is being manipulated in with the same script to kill people for Guy Pierce's version of Dr. Evil. So we have to suffer iterations of that script. Unlike Groundhog Day, Vin's character doesn't remember them, so there is no building of anything, just a lot of rinse and repeat until a climactic final battle.
So in the end we have a whole lot of cyborg fights (the bad guys have enhancements too) with nothing at stake, and a ridiculous ending that's more laughable than evocative. With a six-pack, this movie is probably awesome.