The overall story of Yatterman, for those of you unfamiliar, is that two teenagers-- Gan-chan and his girlfriend Ai-chan --build a giant dog robot called Yatterwolf. Every week they do battle with a trio of thieves called the Doronbows, which consist of the sexy Doronjo-sama (translated in this film as Lady Doronjo) and her henchmen/punchlines Boyakky and Tonzura. In the film, this weekly battle is interrupted by the Doronbows' master, Skullobey, who pushes them to find the Skull Stones to restore him to the world and cause chaos and stuff. Yatterman, which actually refers to the trio of No. 1 (Gan-chan), No. 2 (Ai-chan), and Yatterwoof, of course, is determined to stop them. The original show is a bright, colorful, goofy series, and the new film sticks with the same basic feel.
That aside...okay, let me say that I really enjoyed the film. I enjoyed it in the same way I enjoyed Speed Racer: it stays with the campy feel of the original series, but added a wink and a tongue in cheek here and there.
That said, I don't think that the movie would fare well in mainstream America. In Japan it's a film that's okay for kids, based on a kids' TV show. In America, we don't put giant robots with "Titty Missiles" in films for our kids. Or let one character cheer another on for walking around sans any clothing from the waist down because "everyone goes wild when overseas" (or something to that effect). So, it's not really kid-friendly by American standards...and it's a bit too campy and over-the-top for most adults unfamiliar with Japan's extremely presentational style of comedic acting, I think...not to mention unusual pacing. The focus of a scene is almost always on little things that most American directors would try to keep 'subtle' (like, it's a lengthy scene of two characters contemplating a kiss with voice-overs, rather than the mutual glance I'd expect to see in a Hollywood flick)...whereas the plot elements that you would expect to be focused on, like, um, ANY of the plot tends to get glossed over pretty quickly. The plot is not the point here. Everyone in Japan already knows the plot.
So, the long and short is: if you like super-campy stuff, awesome CG, and/or Sho Sakurai (who IS gorgeous), you'll probably love Yatterman. If you hate overacting, heavy use of CG robots, and/or pretty boys, you probably won't be into it. If you're somewhere in between? I'd say you should go ahead and give it a shot if you find a convenient opportunity, but you probably won't want to spend any serious bucks to take home a copy. (That said, we don't yet know what the US distribution plans for the film are, so I don't know how easy it'll be.) And as for mainstream America, it would probably take too much editing to make it kid-friendly, and it's not the kind of thing your average American adult is likely to want to go see.