It does look nice, but indeed -- it seems to not have much new to offer, apart from the artwork. Cool if you don't already have the albums, though.
I wish they had put the bonus tracks on separate discs (or on just one separate disc), or had at least given a larger time gap between the end of the albums and the bonus tracks. Something new and exclusive might've been good too, as well as the inclusion of the individual booklets for each album. Then maybe I would be more interested in getting this.
Also, I think it's not unreasonable that this box set is being released -- these albums were never released in Japan before. (This is a Japanese box set.)