On the topic of the Wii U's backwards compatibility, we can at least say it's better than the PS3 and PS2 situation.
The problem is that going from Gamecube to Wii was 100% perfect backwards compatibility, barring the LAN adapter support which hardly anyone used. It booted the games straight from the disc channel just like Wii games.
However going from Wii to Wii U we are forced to boot into a Wii simulation mode which is slow and very jarring. Especially as Wii games STILL didn't have a persistent OS in the background (Wii games gave the illusion of multi-tasking, but the home menu was actually embedded in every game), this seems like a very unnecessary compromise.
Worse still we again lost online functionality, except unlike the Gamecube where hardly anyone used it, on Wii LOTS of people were using it. Nintendo deliberately made Connect24 a major selling point of the Wii as the living room console, then stripped it out of the Wii U entirely.
I have credit on my Wii in the shop channel and was going to buy some games and gift them to my Wii U. As the Wii U doesn't have a friend code, not even in Wii mode, I cannot do that. Plus I am unable to send messages to my Wii friends. That is just plain stupid and is not going to win them many friends from people coming from Wii who might use that functionality.