I like them a lot. Not your typical J-Pop girl group more J-Rock. Actually, I’d be hard pressed to classify them which is why I like them. They often borrow from other groups sounds so they sound comfortably familiar but they blend it with there own style. Here are a couple of links that can do more justice explaining than I can. Wiki
I like all their CDs but “Nice” and “An Illustrated History” are my favorites (“Nice” being tops). Nice An Illustrated History
I first noticed them from their cartoon “Hi Hi Puffy Ami Yumi.” It was a tad energetic and colorful and much funnier than it had any right to be, animated similar to the “Power Puff Girls.” (Ok, I’m big into cartoons).