Yes, keep saving them. The 9 + bonus for 7 is worth the wait. Epic was different because it cost more, but it increased your chances (allegedly) of getting a top level rare old drop, but at a 1 for 3 rate. On the Mega, your chances of getting everything are the same...which is to say <1%. However, it will tick a lot of boxes on the 'open 15' feats, and potentially fill in missing gear or emblem feats you might need, or can sell to someone else. I wouldn't hold my breath hoping for an Ivy Flower or whatever the 'top' item is per capsule though....even if you open 15 mega, that's only 15 shots at 9 capsules worth of <1%. Honestly a big difference is what's in the bonus box. The first bonus boxes of accessories and powerset auras held a good value....the later ones with the mercurian flames and such have not. They may do another 'revisit' of the old styles too, which waters down the value some, but if you pick up a Black Hole accessory or Scorching aura you can still do pretty good and it will stack on top of what you pull out of the other 9 TCs.