Well, I'm not sure what to think. My initial reaction was to be rather disappointed, as Spirits are seemingly just ways to power up your character, which is something I never really liked nor got the hang of in Smash 4. At first, it looked like this was just a coat of whitewash over that idea. I guess I was in a mood to be disappointed after the dis-inclusion of trophies and the reveal of the last two characters (nothing against the characters, its just a shame they were spoiled for us, and after hanging around here for a while, its hard not to want a few more). I really hope that the Spirits have trophy-like snippets of information about them, just to ease the pain of losing that particular hallmark.
As they went into the details about the fights you have to do to get them, I was a little more interested. I love event matches, and the thought that there would be fights like that to commemorate various characters was cool. I loved the ones they showed, and despite not containing the actual characters they had some of their personality shine through. I'm also glad to see assist trophies will have a role, I see them so rarely in regular Smash, so it will be nice to see a place where they shine.
The hints of adventure mode showed at the end also did a little to ameliorate my feelings. The CGI opening was great (although I doubt we'll see much more of that, sadly) and what was shown of the overworld map was nice. I'm still a bit disappointed there will be no Smash Run inspired Adventure Mode, which is something I've been wanting for a long time, but I can't let that get in the way of trying something new.
So, in the end, I don't have much love for the Spirit items in and of themselves, as I don't really care about powering up my characters, but some of the elements surrounding them, like the fights to get them and the Adventure Mode, are at least a little appealing. My final judgment will ultimately have to wait until I get the game, of course. We'll see what they add up to when I finally get my hands on them.