I realized why character reveals are the most important updates...
If there's one thing I've learned from studying previews of games to death, it's that one can never gauge anything about how a game actually plays without actually playing it him/herself. My best examples are SSBM and World of Warcraft. In both cases, I had gotten an idea in my head about how a game played and found that, in reality, the game was completely different from what I expected.
Updates which focus on gameplay, final smashes, moves, etc. all need to be tested in order to be understood. A final smash can look absolutely badass and yet be almost completely worthless in practice, but we won't know that until we play the game for ourselves, and probably won't REALLY know until we've had a good deal of game time under our belts (ie. everyone figures out a way to avoid a final smash and it's considered worthless from then on).
Character reveals, on the other hand, are definite. For example, King Dedede's reveal confirmed that he is in the game. We know nothing else, but we know that his likeness and character will be present in SSBB. How he plays, how his moves work in an actual gameplay context, etc. are still very much up in the air, but we KNOW that Dedede is in the game and you will be able to play as him.
That is THE most certain thing we can find out through updates. We only have snippets of music so we don't know if the whole song is good or not. Levels can look crazy but we won't know for certain because we don't have first-hand knowledge of how the physics of the game will relate to those levels.
The ONLY certainty in SSBB which we can know without playing it is the roster, period. Online could be laggy and unplayable, stickers could be boring, spectator mode could suck, the level editor could be clunky and buggy, but if they tell us Sonic is in the game, we KNOW FOR CERTAIN that he is in the damn game.
Anything else is speculation and invites disappointment. I was excited about the level editor but I was wrong in being so. Until I've felt how it plays, I'm just inviting disappointment.