So I tried to get on several times this weekend, but sadly kept getting the same error. The Wii U does get online, but somehow can't connect with individual users (the Friends List gives the same error). Thinking it might be a router problem. A little bit of a bummer really, had kinda hoped to experience a Splatfest at least once.
Oh well, not like I don't have a pile of other games to get through first!