If the rumor of cloud storage for Wii U was true and only had 512MB of space, I could see it being handy for when you carry your tablet to a friends house and want to log into your own profile.
Now I don't know how it will work in reality, but I have a pretty solid imagination. So I see it working as such; Your Wii U is at home wirelessly connected to the internet while you have your uMote over at your friends house synced to his Wii U. You log into your profile which loads your Mii and User data off your personal cloud storage, assuming that wasn't already stored on the uMote's internal memory.
Your friend pops in Madden 2013 and starts loading his custom roster complete with custom uniforms and a custom stadium.
This is where your 512MB of cloud storage comes into play.
Since you are logged into your profile on your uMote on someone elses Wii U, your account recognizes that you also own Madden 2013 and pulls your save game from your console down to the cloud and then pushes it to your new location so that you also have access to your custom roster, uniforms & stadium even though you didn't plan ahead to play Madden 2013 by bringing a memory card with you. And because you are connected to the cloud, that data is automatically updated back to your Wii U at home when you are done. So it is forever recorded that you spanked your friend from endzone to endzone on both of your saves and not just his.
If that was how the 512MB of could storage was used, then I think 512MB should be plenty. If it's meant to replace personal storage all together, then Nintendo will need to rethink that strategy.
oh and I have an article published on the front page:
http://www.nintendoworldreport.com/forums/index.php?topic=37764.0