Miis on their own are a bit weak because they're just a little display object. Their little social network Miiverse holds a fair amount of content though.
Also, Nintendo has said that they won't be allowing you to see customized Miis when fighting other people online in SSB unless they're a friend of yours, probably to prevent copyright (and objectionable content) issues.
Also, Nintendo has said that they won't be allowing you to see customized Miis when fighting other people online in SSB unless they're a friend of yours, probably to prevent copyright (and objectionable content) issues.