Not much!
The squid-ink-game used wuublet to some degree, and there's the Miyamoto (experimental?) games, but even Nintendo itself seems to have a lot of trouble using the thing effectively.
I don't think that's their style. I think they'll hold out until the bitter end, or at least until they get a decent set of software out that can get the ball rolling somewhat rapidly at least.
The squid-ink-game actually looks rather amazing btw and could be a monster hit amongst those enjoying multiplayer gaming. The cute art style should also make the game more universally acceptable, heh, but even with the cute bogging it down it looks REALLY GOOD actually. Very very well designed graphics, and gameplay looks super tight and slick (no pun intended.)
Eight people total isn't on the scale of say, Battlefield perhaps which has like, up to 64 players or something? However, it's enough to create interesting team dynamics, and arguably, tighter and more - ahem - fluid team dynamics.
Too bad Nintendo's voice chat functionality and overall online support is so fucking BAD. They really should have built voice chat into the wuu itself and supported the use of the built-in wuublet mic and speakers; I can't believe they dropped the ball on that one. Instead they wanted to force people to shell out for a separate headset. Un-fucking-believable!
It's totally integral in these types of games, so I'm assuming voice chat will still be included for this particular game, but not having global VC in all titles so that friends can talk across games or in the menus and so on is a terrible design fail.
Anyway, to me, this game looks like a bigger hit for Wuu than Mario Kart. Not everyone enjoys racing, while shooters are almost unversal in their appeal amongst modern gamers. With playable characters including both boy- and girl-octopii, it will also have cross-gender appeal (as well as octopus appeal; now Nintendo just has to release a water-resistant wuublet and molluscs everywhere will be able to join in on the action!
)