Basically, it felt to me like the whole last episode fell apart into RTD's OTT-melodrama standards, which is a real fucking shame because the build up had been so good. The most annoying thing for me apart from the Jack = Ten stuff was the fact that they didn't just do the bottom 20% of schools and assume half the kids would stay home rather than send the army chasing after individual children because that makes for ZOMG TRAUMATIC VIEWING (it's not fridge logic if you're shouting at the evil characters to at least be clever evil characters as they're doing it). I also think it is too cynical to think that nobody at all spoke out at COBRA, and that the army all went along with it and stuff.
OK, that was a bit longer than I intended it to be when I started typing. There was good stuff, loads of it, but it looks like yet another case where RTD's ending undermines what's come before it.