I've said before that my attitude towards the Cartel Market is that I don't like to spend real money on top of my subscription, but I'm happy to buy other people's purchases for in-game credits. I do appreciate the added variety that comes from this. However, since I'm not actually keeping a close eye on the in-game store myself, I frequently miss new stuff coming out and don't really notice it until I see someone else use a particular item or piece of gear some time later and go: "Huh, that's neat. I want one of those."
This was the case with the encrypted datacubes as well. I vaguely recall hearing about them some time ago in connection to a burst of outrage about "story content from random packs" but since that quickly died down again I figured that it couldn't have been anything too important.
They came to my attention again the other day when Pet Tank and I were questing on Nar Shaddaa and a look at the group quest log revealed that he had eight missions on the promenade that I didn't have, all of them with nearly identical names. When asked about what they were, he explained that they came from the encrypted datacubes and were supposedly "quite interesting".
My curiosity piqued, I made my way to the GTN and splurged on a full set of all eight cubes myself. They ranged in price from roughly thirty to three hundred thousand credits - not insanely expensive, but not exactly cheap either once you add it all up. Each of them is consumed on use and gives you a quest to go to a terminal on Nar Shaddaa. When you use said terminal, each cube plays a little cut scene from what looks like the Shroud's diary. They don't exactly provide any major revelations, but they do fill in a couple of background details about the Shroud as well as about the Makeb storyline in general. Completing each mission grants a reward choice between an experience or a valor boost, though no XP or credits. (Apparently there used to be a monetary reward option, but typically people found a way of exploiting that by cloning the cubes via collections and then awarding themselves endless free cash on alts, so it had to be removed.) Watching all eight cut scenes on the same character also completes a sort of meta-quest which rewards you with a full set of decent-looking orange gear (except for the silly hat, but what else is new).
If you've got some cash to spare and happily eat up every extra bit of story content that the game provides, I recommend that you pick up a set of these from the GTN while they are still available. (From what I gather they came out of two different packs, in sets of four each, about two months ago, and I guess that like all previous packs they will eventually be retired.) If you find them too pricey however, there's no real need to fret either. Like I said, the whole thing adds a bit of extra detail to the story, but it's nothing essential.
That said, I'm glad that official word from the devs has been that they heard the negative feedback about story content in packs "loud and clear" and won't be adding any more in the future. It's not so much that I think that extra story content on the Cartel Market is a terrible idea (though I'm not a fan of it; I still expect to get automatic access to most things as a subscriber), but I do think that it's not something that should go into the Cartel packs. In my opinion story updates (even really minor ones) shouldn't be something that's distributed at random, and even less so when said random distribution method will eventually be retired, making the content disappear from the market and unavailable to new players in the future.