Yep. I love it.
Cartoonish? I wouldn't say so. Its style of animation is different from most anime I suppose. A bit... brighter, more fluid, I guess.
No big deal though. It's a movie that I don't expect people to like quite as much as I do. It just gets to me on some deep down, personal level. I love the story, the moral ambiguity of the whole situation, the characters, etc. I just love the movie.
And you're right about "Fireflies". Pretty gutsy film when you think about it. I bet even most Japanese filmmakers wouldn't want to tackle that story as an animation. It would NEVER get made in Hollywood. Even if Hollywood started making anime style films, they wouldn't make a "Grave of the Fireflies".
And it's true, American cartoons are taking on anime aspects. The eyes are most notable.
"Taking on Japanese stylings"?
Little animation has been done in America for decades. Even Japan farms it out now.
Easier on the art team. Lousy for a viewer seeking some variety.