Given that Let's Kill Hitler is a pretty solid follow-up to A Good Man Goes to War and does it with such an audacious and provocative title, you'd think I'd like this episode or at least that it would be more memorable.  It's a real disappointment though.  I find the title and really the whole Third Reich winds up being a background detail to the much bigger focus on River and the funny robot piloted by shrunken down soldiers.  These things and the whole Hitler angle leads to a lot of fun jokes and good little moments, but the episode feels more like a delivery vessel for Moffat's writing more than a cohesive or coherent narrative.  It's alright - carried by its outstanding cast as all our main characters get to shine here and the little moments.  It's weird, for example, that a childhood friend of Amy's is actually River's previous body, but it could have been interesting.  I feel the consequences and effect this has on Amy is pretty minimal, though.  This episode is really just about the River and the Doctor, and though it is weighed down by all the weird stuff with the robot, it is neat how River is kind of the one off-foot in this story, and knows far less than the Doctor this time around.  It leads to a great shift in their relationship that helps define an episode that all-too often lacked direction.  So, yeah, just like A Good Man Goes to War, this had a lot of potential, but wasn't quite fully realized.