This is how my friend recommended this series to me: "The girls are guns. 'Nuff said."
Of course, he had only seen the first episode. I decided to check it out because, hey, the girls are guns, 'nuff said. So I watched the first episode and was met by a show with a lot of promise. A catchy OP, some fanservice and amusing innuendo regarding guns, an interesting premise....
And then, a few episodes later, I had sort of given up.
You see, Upotte!! contains girls who are anthromorphic guns. Now, while some series would take this concept and make it ridiculous and fun, Upotte!! quickly makes it clear that it's about guns. It frequently goes into explicit detail about the guns. Now, maybe this is enjoyable to some people. Maybe some people actually care. But me? I'm not a gun guy. I couldn't care less about different models. I think that an entry under Widget Series puts it best: "anime viewers who like moe [a sort of loosely defined "cute" visual style] will be put off by the guns, and gun fans
will most likely be put off by the moe. Only those who can appreciate--or tolerate--both genres will be able to watch this show." In addition, a lot of the humor is pun-based, and there are obviously some puns that don't translate very well. There's fanservice, but it's almost not worth the time spent slogging through gun facts.
Really, I've come to the realization that it's basically Hetalia with guns instead of countries and yuri instead of yaoi. If that's what you like, good for you. Go watch your show about cute gun girls. But anyone else will probably find it pretty boring once the novelty of the first episode or two wears off.