The first thing I noticed about the art and animation was that there wasn't really much of it. There are a lot of repeated movements and people who float without moving their legs, but it doesn't look cheap or badly done. It fits well with the comedy in the show, because it's pretty silly. Also, the character designs are good. They're all similar to the originals in the manga, and they're very cute.
As for sound, I liked all of the voice acting. The voices fit the characters well, except I wasn't impressed with America's voice. I did really like that the anime kept most of the original dialogue, and that there is no filler. The soundtrack is pretty simple, and it adds to the non-serious mood of the show.
When watching this show, I find it's easy to follow and very funny. I often laugh out loud while watching it (which I don't usually do when watching anime). Also, the parts about America's storage cleaning were beautifully done. I would like to see England appear more in the anime though.
Overall, Hetalia is wonderful. It's quite possibly one of my all-time favorite animes, and I look forward to seeing the rest of it after it is subbed.
