Outside of the club Nintendo deal with Mewtwo, I haven't gotten any of the DLC. My friend even pre-ordered Splatoon and offered me the DLC costumes, but I wasn't really interested in that either.
I will eventually get all the characters and stages, then perhaps some mii fighter costumes.
That all said, I think the DLC for Smash has been bad. Not the worst or downright terrible, but just bad. It initially didn't seem that bad to me, but the flow of DLC makes the price really pile up. I'm honestly surprised on that end.
I think they have a reason for the continuous DLC and perhaps the price point here and there, but so far its all really speculation on my part so I'll hold off on my conspiracy theories for now








