Ok, first I'll admit this piece of review will be one of the most biased things you'll ever read because, when you look into my profile, you'll see that it's my 2nd top favorite anime. I usually try to be objective, but really whenever I think about this anime I only see awesome in it, but anyway here goes:
Story: Unrated/10:
I usually just leave story unrated because, as I like moe, slice-of-life anime, they usually don't even have a real story at all, and to be frank they don't need it. As for Girls und Panzer, the whole story can be summed up at this:
WARNING! SPOILERS AHEAD!
"Miho messed up in the last Senshadou Tournament Finals and costed her school the victory (...in order to save a drowning teammate)! She's so shamed that she decided to move to a small school without Senshadou. There's just one problem: the school's so small it's going to be closed unless it has an epic victory, so its Student Council President re-opened Senshadou and forced Miho to join, where she must command her school to victory in this year's tournament in order to save her new school as well as prove her worth to her own family (which she eventually succeeded)!"
SPOILER END!
So there.
Animation: 10/10
Not sure what you think, but I personally think the animation in this series is perfect. Sure it may not be as shiny as, say, KyoAni's moe masterpieces, but it works. I reckon it'd look pretty strange if everything looks dreamy and brilliant to the Clannad level, but it's gorgeous in its own ways. The characters look cute, the scenery looks vivid, and I couldn't find any imperfection in the animation itself, especially the tanks', they are just glorious yet so believable (except for the speed buff in everything but uh... that's another story).
Sound: 9/10
This anime has some of the best songs and soundtracks I've heard, the glorious OP DreamRiser for example, and I'm not even very fond of marching music. Besides, the sounds the tanks make (tracks sound, turret traverse sounds, GUN sounds, oh the gun sounds...) are all pleasing to the ears, I can understand perfectly well why "Firing the tank's cannon for the first time is shown to be intensely pleasurable for Saori, Hana, and Yukari" (according to TVTropes). As for the voice acting, I'm not so good at analyzing that, but I'll just say none of the voices sounded annoying or fake to me. My only qualm is that Shirou remixed the main theme (apparently called "Panzer vor!" if I'm right) a little too much.
Characters: 10/10
Ok, most reviews before me said that the characters weren't too interesting and were shallow, but consider this: It's a 12-episode anime, with 4 fully-shown tank battles lasting 2-3 episodes each, plus a training match. See? It's not like those overly-long action animes where you can "develop" your characters however much you want because you always have time. And then, GuP has a LARGE BUNCH of characters, since there're many teams and each team (if you count each rival school as a single team, then there're TWELVE teams in total, and I'm not counting Anzio) is composed of 3-5 chars. The very fact that not many of them are copies of one another at all is already a merit.
And yet, it manages to be quite the opposite, while the characters are not deep in overly-complicated ways like you often see in long action or drama animes, their traits were executed quite well. They're not all Ms. Troubled Life, but they're who they are.
WARNING! SPOILERS AHEAD!
Yukari is a tank nut who's extremely loyal to Miho, Miho is a gentle yet genius strategist, Saori is someone with a good tongue who's crazy about love, Mako is a lazy-as-s...eh...sloth genius, Anzu is an extremely easy-going manager who actually cares a lot about her teammates and always micro-managing everything in the background for the best, Momo is extremely loud yet considerate and determined, Darjeeling is someone who always act elegant and tell nice-sounding quotes even her best friend can't understand, Karina is a shy and a bit noisy girl but is also actually quite passionate when her teammates are concerned, and the list goes on...
SPOILERS END!
Some of the characters' eh... character are fleshed out in just one single scene, and sometimes that's all she needs.
Enjoyment: 9.5/10
The tanks battles actually gave me some of the best thrills in my life that normal action animes couldn't, and I enjoyed it all while assured that none of the characters will actually be harmed (because I'm just that much of a coward and a light-hearted person, plus none of the characters deserve to be harmed), since there was an explanation on how no one can actually be killed in the sport (although I gotta admit that was a half-assed explanation that kinda came out of nowhere, but hey at least there's an explanation that at least sounds plausible).
Plus, the breathers episode were well placed and very relaxing, plus they helped a lot with character development, like a true slice-of-life anime. I hated how everyone just rated this anime with action criteria, since this is clearly an action-sports-slice-of-life hybrid.
Oh, and I said it gave the kind of thrills normal action animes couldn't. You know why? Because everything was handled realistically. Ok, it may not be too realistic when the exact specs of the tanks are strictly concerned, but they were worked out with very believable tactics and real teamwork. Whenever Ooarai wins, it actually felt like they won, not like they-won-because-the-author-wanted-them-to, which I think is the problem with most action animes. In those animes, in times of need, the "heroes" always get some s...uh...special powers that help them win magically because "power of friendship" and "protecting something" or "determination" or some s...stuff, or just plainly because the author wanted it.
WARNING! SPOILERS AHEAD!
My only qualm is that in most of Ooarai's victories, the rival schools give them too much of an advantage, but it's all firmly explained. Also, in most victories, Ooarai and the rival school shoot at the same time at each other's flag tanks, and then Ooarai hits first.
SPOILER END!
Misc. Things:
I like the (SPOILER?) school ships.
It's obviously set in another universe, so please don't judge too much. You may never know what people outside your group think. Besides, it's been explained that no one can actually be killed (unless someone shoots someone else or run him/her, most likely her, over on purpose but that's considered murder normally).
Overall: 10/10 (Rounded score, but still...)