I dig 'em, and I was surprised because I was sure I wouldn't. (So far, there is only one Japanese band I don't care for at all, after repeated attempts to redeem themselves. Everybody else is passing the introductory check with me.)
Anyway, B'z are not what people think of j-rock, typically, but I wouldn't stick them into j-pop necessarily either just due to their major influences on decidedly non-j-poppy bands. Definently no goth or opera-y stuff or any fun disturbing vocal effects for them. Not really any ballads in the normal sense either. More along the vacation-y 80's sorta rock. Upbeat, but not hyper...good for happy fun music when you don't feel like bemani stuff. They fill a similiar mood niche for me as TMR does, I guess, but with a very different production sound. B'z certainly have got variety tho, so it's hard to get bored. They've got like 160 songs or something, more? They really cranked those out. Between them and Glay...
Still, worthwhile stuff and a nice break from when Mana or Kaoru have been hypnotizing you for hours with their lovely darkness.
Love Phantom, Bad Communication...hehe, there's great engrish there. Some of the best non-anime songs examples I can think of. I like Ring and Juice, too.