Doctor Who is arguably more of a fantasy show than a science-fiction one. However, this doesn't stop it from from having "sci-fi" episodes and this was one of them.
Exploring the themes of "surrogate bodies" and identity, "The Rebel Flesh" involves Team TARDIS arriving at a factory on 22nd century Earth just before it's hit by a solar tsunami (of which more later). The dangerous work is done through created bodies controlled by human operators known as "Gangers". When the tsunami hits, the gangers become living people of their own...
"The Rebel Flesh" is a rather different episode from the previous four of Season 31. Instead of being big and bombastic, it focusses on moral issues, like quite a few of the great stories over the years, such as "Doctor Who and The Silurians", "The Ambassadors of Death" and "Genesis of the Daleks".
On this form, I don't think the story is going to join the pantheon of true greats, but neither is it going to end up in the pit of shame like "Timelash" or "Warriors of the Deep".
Matthew Graham's done a good story here, making us think about our views of clones and AI duplicates, which we too often dismiss as cheap plot devices and don't really feel for as they're not "real". The Gangers feel very much real and should be considered as such. Matt Smith turns in a quiet, understated performance, not overdoing things - in fact he's a little too subtle at times. Everyone else, including Marshall Lancaster and Sarah Smith, do well and the pre-titles sequence is good in particular.
There are two flaws in the story. I've heard of solar flares, but I've never even heard of a solar tsunami. Without some decent explanation, it sounds stupidly unscientific (yes, I know this a show with a time travelling spaceship that's bigger on the inside) and a power failure, plus attendant earthquakes, could have been caused by, well, an earthquake...
Secondly, the pacing seems a bit slow for my liking. While Who doesn't have to always be a huge rush, this story seemed to be going for the pace of the classic era and it didn't always work.
I'll see how "The Almost People" goes, but so far this isn't brilliant, it's merely good.