In my opinion if the story calls for a 15 minute episode and it works, I'm all for it. We've seen how successful Moffat can be with single-parters. Blink, Girl in the Fireplace, A Good Man Goes to War, etc. The Doctor's Wife, of course (not his but produced under his watch, ditto Vincent and the Doctor). Moffat also gave us the Library and Empty Child 2-parters which were acclaimed, so it's not as if he can't do two-parters. But clearly he finds more satisfaction in single-chapter stories and proved it's possible to deliver a satisfying season finale in one hour (granted, the revival's format of having background arcs helped get some of the exposition out of the way in earlier episodes). So if it works, and the stories work, and if it means getting 13 different stories rather than 6, I'm happy with that, and I'd be happy if it was a 13-parter.
I don't think the "BBC America wasn't happy" argument holds water. Nothing prevented them from keeping the show on for the holiday. After all when are they showing the Christmas special this year? What's the difference between the break happening between a two-parter and between standalones? A break is a break. If they're so upset about it they should have pushed the BBC to preempt Doctor Who that weekend, or pushed the BBC to begin airing Doctor Who earlier or later in the year to avoid it. I can't imagine they were very cheery about the split season idea anyway.
Speaking of which, does Moffat indicate whether that's happening again next year? Narratively I had no problem with the split season this year, but it really did make the season seem a lot shorter and, in some respects, less epic than if they'd gone 13 weeks straight.
Yeah, but I'm an American. I like my seasons to have lots and lots of episodes!
Perhaps, but there is such a thing as quality over quantity. Even at 13 episodes Doctor Who delivers the occasional dud, to be sure, but look at the history of Star Trek - every series (no exception, including DS9) could be reduced down by almost a complete season's worth of episodes if you omitted episodes produced simply as filler or ones that turned out as garbage because they didn't have the time or budget to do the story justice. The epitome of this was with Lost in Space - the fellow who played Dr. Smith was once asked why they ended up doing an episode with giant talking carrots, and the actor said it was because they completely ran out of ideas. If Lost in Space only had to worry about 13 episodes it would have been a much stronger series because they wouldn't have had to produce episodes like that. And TOS probably would have had no need to foist "Spock's Brain" on us; DS9 "Prophet and Lace"; Enterprise "A Night in Sickbay"; TNG "Shades of Grey" and half of season 1; Voyager (too many to list)...
Indeed, the ideas of the "flashback episode", the "catch-up episode", and the "bottle episode" were all because of the need to fill time. And for every "Midnight" that actually works (Doctor Who's Hugo-nominated bottle) there are tons of others like Shades of Grey (TNG's infamous flashbacker) that don't.
Alex