This series has very quickly become one of my favourites ever.
I am both an anime nerd and a bit of a history nerd, so when I heard of this new manga that had all the countries of the world getting a representative and telling historical facts through comedy back in October 2008, I just had to check it out.
Hetalia is actually quite educational, although there are times when the history is somewhat innacurate; but forgiveable.
There isn't much of a story, as the characters weave in and out of silly historical situations, but you will be hooked. It's a fix.
The artwork, I think is very pretty. Very bright, it jumps out of the screen at you and while the animation isn't the best I've ever seen in an anime, it's sufficient.
I adore each and every character of this series. Normally in media, there's a character you hate, a character you obsess over, and a character who you like because you can relate with them. Hetalia has all those and a sprinkling of cuteness just to keep your interest. My favourite characters are France, Russia, Poland, Lithuania, America, Canada, England, Austria, North Italy, and Hungary.
When the anime came around, I was so excited and watching the anime fills in my Tuesday evenings/Wednesday afternoons. It's awesome. I was once watching it in the living room and laughing so hard I was crying (this was episode 6 I believe, with the Allies making smores and America screaming that France's camp-fire song sounded like a demon summon), and my dad even asked me what the hell was making me laugh so much. It's such a morale boost before I do my homework.
Overall, I would give this series a 9. This review may be biased because I'm such a huge fan, but I do accept that there are some historical innacuracies. But on the whole, it's fun, educational, sweet... I love it.