Not going to comment on the show itself, since if you're buying a complete set you're probably pretty sure you like it anyway, so I'll just review the package itself.
Inside the box are 18 individual DVD boxes, with 2 discs in each. When lined up, the spines make the "X" logo, and it all looks fine. Definitely better than the ugly single season sets, anyway.
The box itself is the problem. You CANNOT stand it vertically on a shelf, as the lid only stays shut under it's own weight, there's no catch or anything. There's a little circle of something underneath the X logo on the front, which looks like it's meant to stick to the X and hold it shut, but it isn't sticky at all, it's just a circle of clear plastic, so it doesn't really do anything. Only reason for it being there I can figure is too stop the pieces of cardboard from actually touching, although I'm not sure why this would be an issue.
It's also worth noting there are no special features, and no little booklets or anything of that sort which are often included with complete box sets.
Still, for the money, this is the one to go for. Less-than-perfect packaging isn't a fatal flaw, it's just a minor inconvenience.