The only set I've gotten so far is the Braves set, but I can generalize a little about the other sets based on it. Each set has 29-30 cards in their base set and all the sets use essentially the same format. Unlike pretty much every other BBM card I can think of, these cards do not have a glossy finish on the front but instead sport a matte finish. BBM is going for an oldies look with these sets and I think they've pulled it off pretty well:
|#07 Hisashi Yamada|
|#18 Kiyoshi Morimoto|
|#12 Shinji Nakazawa|
|#27 Yutaka Fukumoto|
|Back of #27 Yutaka Fukumoto|
The significant thing about the backs (besides the fact that they don't have the player's picture on it unlike most BBM issues) is that they feel like the back of old (pre-1992) Topps cards. I half expect to find a card with a bubble gum or wax stain on it.
As for the set contents itself, it's a decent representation of the 1970's & 80's era Hankyu Braves. The main stars (Hisashi Yamada, Yutaka Fukumoto, Takashi Yamaguchi, Hideji Kato, etc) are included as well as the significant foreign players (Bobby Marcano, Boomer Wells and Bernie Williams). The set also includes manager Toshiharu Ueda. My only real complaint with the set isn't really about the set - it's just that this era of the Braves has been mined for OB sets by BBM a couple of times already in the last five years.
I should mention that the unopened box comes with a plethora of possible autograph cards, both authentic and facsimile. I, as usual, got an opened box.
Ryan has already done a post on this set (as well as the Hawks set) and you can see all the cards at Jambalaya.