When I finished Hetalia: Axis Powers Volume 1, I hesitated to review it. However, I'm sure that manga fans can be reasonable, and accept some criticism, so why not?
Parts of Hetalia were extremely funny. It's hilarious to see characters based mostly on (Japanese) stereotypes of countries, and the interaction between countries is very amusing. Each country involved in WWII is personified as young men, containing all of the stereotypes of personality that the country brings to mind. France is a cowardly fool, Germany is arrogant (and a little bit of a perv?) and America is brash and thinks too much of himself. The title character of Italy is divided between Northern Italy (Italy Veneziano) and Southern Italy (Italy Romano), harkening back to the relatively recent unification of Italy a century previous.
The story takes place some time between WWI and WWII, as the countries are getting to know one another in their current configurations, and friendships and fights spring up around the most petty things.
Watching the countries interact, especially with the liberal use of footnotes on nearly every page, is certainly funny to anyone who has even a passing interest in international politics. Yes, at time, it seems like the leaders of other countries are acting like petulant brats, so it's fun to watch all the countries try to queue up at a grocery store.
The only reason I can't give this a firm recommendation is the absolutely horrendous artwork. This started as a webcomic, and was never cleaned up for book release. At times, it's even a bit hard to keep track of which characters are in the panel, as the art is so sketchy. I stopped and restarted the first volume several times in frustration at the artwork.
If you're more patient than me, Hetalia: Axis Powers Volume 1 has quite a lot of potential, but perhaps the anime is the best way to take in the series.
Highs: The humor is right up my alley, with 'it's funny because it's true' moments throughout
Lows: The art is just TERRIBLE. Seriously
Verdict: If you can tolerate looking at it, enjoy. Otherwise, check out the anime
Further Reading: Neko Ramen Volume 1, Maison Ikkoku Volume 1