This is another one of those stories that gets a rough ride from fandom, but -- at least on the basis of these first two episodes -- it's hard to see why. It's no worse than anything else we've seen under Graham Williams's producership, and there's quite a lot to enjoy here. The propaganda video is honestly a nice touch, juxtaposed as it is with the scenes of despair and destruction we see in the makeshift hospital on Atrios. I also like the iridescent quality of the braids and such on the Atrian costumes. I'm less convinced about using an office chair as the Marshal's seat of power though.
See, the thing is that these episodes are structured quite well, and no one really lets down the side on the acting front; people often deride Davyd Harries, but here, at least, he's quite pleasantly understated. The worst of them is probably Ian Saynor as Merak, and that's only because the script needs him to be all moony over Princess Astra. And this is probably Mary Tamm's best performance as Romana, as she's finally figured out how to deliver the exposition lines in a way that sounds natural (a problem that she was having in earlier stories). Plus there's a lot of fun to be had with John Woodvine's performance as the seemingly possessed Marshal of Atrios, constantly fingering his neck and prone to sudden, irrational mood swings.
It's got a decent set design, a good cast, and a reasonable script (well, except for the second cliffhanger, where the Doctor suspects he's walking into a trap and then seems surprised when the trap is sprung). It's not going out of its way to impress anyone, but so far The Armageddon Factor is a solid, entertaining story.