I'm hoping its more then a marginal improvement over 360/PS3, that developer quoted earlier in the thread says it will be the most powerful system by far on release, which suggests more then just marginal. But then another recent comment from an analyst suggested he'd heard it was only 50% more powerful, so who knows at this stage? Still at least its basically confirmed that its more powerful, we'll have to wait and see by just how much.
Developer = A person who works with hardware and has likely actually seen what the console can do.
Analyst = Someone who speculates based on his beliefs and preferences without any solid fact to back it and has likely know nothing about the console as he would have no more access to information than the rest of us.
I would go with the developer.
Also, I was wondering how much more power the Wii U would have available if it wasn't rendering to two different screens at once?