Even though Steven Moffat knows he's introduced mind-boggling plots into Doctor Who, and will introduce many more, he's confident that viewers will be able to keep up.

At the recent press screening of Let's Kill Hitler, Moffat said: 
Assuming an intelligent audience is a good idea and clearly, going by our ratings, it's a successful idea.

I can't see what's wrong about assuming intelligence in your audience and what's bad news about being rewarded for assuming that. They are clever, they will get it. My nine year old got all of this ages ago.
He also talked about the portrayal of Hitler in the up-coming episode.
Hitler is quite an iconic name to be honest - in an evil and ghastly way. I think my younger son said, 'Won't Hitler be offended?' In Indiana Jones there was a brilliant gag where Indiana Jones accidentally gets Hitler's autograph.

I think if you really want to p**s off Hitler, now that he's dead, you don't make him into an icon of evil, you take the mickey out of him, make him a joke, make him be punched by Rory. I can imagine how cross Adolf would be if he watched the episode.
So basically, if you don't understand his stories, then you're stupid.

Let's Kill Hitler airs on BBC One and BBC HD at 7:10pm on Saturday 27th August.