At launch, the Wii U was bogged down by performance issues and in dire need of a system update. While updates have indeed been made, Nintnedo isn't quite don. Next month we’ll see the release of yet another system update.
What is in the update itself? More improvements to the system's stability and functuality. This won’t be the update that brings the Virtual Console to the system, though. That'll come later this spring.
As always, Nintendo warns us that the update may take up to an hour to download and to not unplug the system during the process.