To be perfectly honest, I think the Wii U as a tablet would be frighteningly good... I mean the specs of the Wii U, whatever they are, should be snappy and produce graphics that outstrip the ipad for the entire generation, even just looking at memory performance of portable devices, it will be a long time before they can really catch up...
Having a browser that is comparable today to what the Wii's was on release would be fine, the interface would be far superior, and youtube should obviously be there, netflix is also confirmed... game wise, I imagine angry birds and more popular apps will have no trouble making it over, and if Nintendo puts some of their mini games on there... it's going to be pretty amazing... This is all just added on to also being an amazing console, I can see the system having a tablet being a major selling point... that is really all I am saying.