Funny you mention the Wii U and 3DS apps. They are just wrapped, unoptimized webkit wrappers. Their webkit versions is old, which is good for the homebrew community; but bad for people that want to use it, since it's so slow and unresponsive.
You can ask any big Twitch partner about Youtube; the ones that bother to comment about it all agree:Ttwitch takes care of their partners better than Youtube. They only upload some content to Youtube because the Twitch VODs don't show up on the Google searches as high.
In the end, everyone else did too little, too late. Twitch got the momentum, and the competitors can barely match the small list of features Twitch already has (such as chat moderation, IRC front-end, a balanced way to send money to content producers that doesn't alienate the viewers, etc).