Basic jist of it: there will be balance changes, changes enough that without the 1.0.4 patch you'll be unable to play multiplayer locally without it. This will also cause any saved replays to no longer work so find a way to archive those amazing matches now.Ver. 1.0.4 [delivery scheduled in November 2014]
I will adjust the game balance.
Other, so who can play comfortably the game, and fix some of the problems.
※ If you download the update data (Ver.1.0.4), and those who use the update data (Ver.1.0.3) previously you will not be able to local communication competition.
The replay data that was saved in the update data (Ver.1.0.3) previously they can not be played back.
※ update data (Ver. 1.0.4) delivery date or later, in order to make the internet play, the update data (Ver. 1.0.4) will be required.
While nothing's solid, many people believe some significant glitches and oddities will be fixed, like Yoshi's Egg-teleport or Wario's complete violation of physics.
UPDATE: A Wii-U firmware patch has been released (5.3.0) that adds Amiibo settings. According to this article, Amiibos will only be able to be loaded with one game's worth of data at a time, so if you were planning on having the Mario Amiibo for both Smash and future titles you better get a second one.
http://www.nintendolife.com/news/2014/1 ... imitations
Should point out that this only applies to games that write data to the figures, not just reading them. When used with Mario Kart and Hyrule Warriors they only read data so there won't be an issue there.