Nintendo comments on slow load times and freezing for the Wii U
I luckily have not experienced any Wii U freezing but I have seen some slow load times between applications. Nintendo has released a generic statement about the issue.
What to do:
Instances of system freezing are rare and unlikely to occur. If your system has frozen unexpectedly, do the following:
Reset your system by unplugging it from the wall for 10 seconds.
Ensure your system is kept current with available system updates
We are aware that users are experiencing load times when they launch or switch between applications. We are exploring ways to enhance features for consumers’ overall experience.