I just picked up Ossu! Tatakae! Ouendan! for the Nintendo DS and noticed that english-language reviews are pretty hard to come by. 1UP's preview
gives you a pretty good idea of what the game's like. Having actually played it, I can tell you it's a lot of fun, as long as you're not one to equate polygon count to fun. I'm not sure how long its appeal will last but a good bit of it is playable without any Japanese knowledge. It even appears to have some multiplayer functionality.
Ouendan! is a rhythm game that has the player tapping and dragging on the touch screen in time with music. There's quite a lot of licensed J-pop in there, although they're probably not the actual artistes. The DS speakers do get a good workout with the music, and unless you're using earphones, you probably won't notice the audio compression. Buttons appear on the screen for you to tap as gradually-shrinking concentric circles cue you in as to the timing. For that reason, it's reminiscent of Technic Beat.
When I bought it, I had no idea that this game was developed by the makers of Gitaroo-man, but in reflection, it makes sense. Unlike Bemani games, iNiS's music games have narratives and characters. The "cheerleaders" in the game are three men in long black jackets, reminiscent of overzealous Japanese school pep squad leaders. Their formal appearances, combined with their Power Rangers-ey sentai-anime poses, make for fun juxtapositions. Marching band whistles and cymbals triggered by successful taps add to the cheerleading flavor. Do really well and the background will be lit with flames of passion and close-ups of the cheerers.
While the gameplay is functional and the music is good, one unique element is the game's use of cutscenes. Like Gitaroo-man, bridges in the music are filled with noninteractive animated sequences. However, Ouendan! uses an over-the-top manga/old-fashioned anime style that not only endear the characters to you but also give you an idea of how you're doing. If you play well, the characters accomplish epic-level challenges of the most everyday sort that bring them closer to forming their romances or completing their homework, with a big "O" or "X" capping each cutscene to let you know if you've done well or poorly. These breaks in incessant screen-tapping are also a good chance to give your eyelids a short rest.
Games don't get more culturally specific than Ouendan! but, if you dig bold manga art and the sound of J-pop and are looking for a rhythm game for your DS, you can't miss this one. You'll even be able to play it on your US-bought handheld without a hack.