The TOS, TAS, and ENTERPRISE packaging are the best. At least they're in a hard shell case, and once you figure out how to open and close them, it's no problem.
I don't mind the TNG cases. At least they are study, and the foldouts don't bother me, but yeah, a little more thought could have gone into those. Such as a hard shell case.
The Voyager packagaing....I'm surprised those have held up, they're so flimsy. I keep expecting them to fall apart, but so far, so good.
DS9........good God. I don't know what the hell the guys who made those were smoking, but it had to be something powerful if they those these cases were a good idea. So far, season 5 is the only one that hasn't fallen apart, and I have used roughly eight or nine miles of scotch tape to keep the other six sets together. I'll bet that was the plan. Paramount had a deal with a company that makes scotch tape. They would put DS9 in the shittiest cases they could make so buyers would in turn have to buy tape to keep them together.