Dragon Ball/Dragon Ball Z/Dragon Ball GT seems to be the only series/franchise besides Neon Genesis Evangelion that I don't mind rebuying. For Dragon Ball Z have the original edited Pioneer releases containing episodes "1"-"53", the FUNimation Uncut singles from episodes "54"-"276", the nine Ultimate Uncut releases from FUNimation containing the first 3/4 of the Saiyan/Vegeta Saga, the 9 orange brick season sets with the widescreen formatted picture, and am currently collecting the Dragon Box Z sets. I also have the first 3 films released by Pioneer, the 13 films as released by FUNimation the first time, the two specials, and all of the steel cased releases of the specials and movies. I will also be purchasing Dragon Ball Z Kai upon its release. I don't know what it is about the series/franchise, but I can't get enough of it. If there is ever another release, I could see myself purchasing it yet again if it's anything different from previous releases.
I can say that the Dragon Box Z sets have the best quality picture I have ever seen for the series, and I am satisfied with my purchase of the first 2 of what will probably be 7 sets. The hardcover books are also very cool little premiums. I'm not saying that they alone encourage the purchase, though. They are in no way on their own worth the $40-80 you will spend on each set, depending on where you purchase them. Whether you've purchased Dragon Ball Z once or not at all, I can say that if you want to own the series in its original format, uncut, and restored to look brand new, this is the way to go, at least until the next release if there is one.