I haven't used it but can't you also not link a Wii account and you have to re-buy all the stuff you bought on the Wii?
Nope.
Wii doesn't have a user account system, but all your eshop and Virtual Console games can be transfered over and played on the Wii U for free. Same for DSiware games transfered to the 3DS.
You can pay $1 upgrade fee for VC games if you want the new Wii U features but you don't have to, if you just want to play all your old games on the new console.