Humor will not be tolerated!! -Portia

I saw a McDonald's ad that said 'Kinda Hungry?' with the Spanish translation underneath 'Medio Hambriento?' Is ser hambriento (e.g., soy hambriento) just as grammatically correct as tener hambre (e.g., tengo hambre)? I've only ever heard the latter.

It is estar hambriento (estoy hambriento) (ser would be a very unusual usage), but it is grammatically correct, though not as common. It is something that you would see in older texts, such as the scriptures, so it might sound kind of funny to a lot of Spanish speakers, but they would understand what it means.

It actually can be used with many verbs; the closest translation of the work is "starving" although "hungry" also works. "Hambre" more closely translates as "hunger." "Medio Hambriento" would probably more closely translate as "half starving?"

To put an English approximation on it, it might be like saying "Are you hungry?" versus "Do you have hunger?" Both are technically correct, but the latter sounds wierd, or even archaic as fred pointed out.

Kind of flip-flopped from English. In English to be hungry is normal and to have hunger is archaic, but in Spanish to have hunger is normal and to be hungry is archaic?

That about sums it up, yeah.

I noticed while in Poland recently that a lot of these fast food slogans are difficult to translate. They either have to sacrifice meaning to retain the quick and easy nature of the slogan, or they have to sacrifice the brevity of the statement to retain a more accurate meaning.

I'd imagine "Yo quiero Taco Bell" worked pretty well, though.