How does your Wii U work with your old Wii data? Here are some answers.
1. How does the transfer process work?
It's very simple, actually. You need to have an SD Card with at least 512 MB on it. After performing your Day 1 system update on your Wii U, there will be an icon for "Wii Mode". Inside that menu option is, surprisingly, a full Wii System Menu. One of the home screen icons will be a Wii U Transfer Tool, which is actually a shortcut to download that tool.
You'll also need to hit up the Wii Shop Channel on your Wii to download a system transfer tool there.
Once you have the system transfer app on both systems, you'll start on your Wii U, and put the SD card in. Run the transfer app, and it will connect to the Internet and prepare your SD card for the transfer. Once this is done, you will be prompted to take your SD card, and put it in your Wii. Run the system transfer tool there, and you will be warned that all of your Wii Shop information will be permanently removed from your Wii.
Click OK, and the magic begins. An army of Pikmin will begin to carry the data from your Wii, and load it onto a rocket ship. This process can take 20 minutes or so, depending on how much data you have. Note that only the items on your Wii System Memory are being copied. All of the WiiWare and Virtual Console games on your SD card are not going to be moved over, however the licenses will be. In order to get these games on your Wii U, you will need to re-download them from the Wii Shop Channel located inside of Wii Mode on your Wii U as the old SD card will not work with it.
After the Pikmin are done loading up your SD Card, your Wii will reboot, free of all of it's purchased content.
The SD Card must be placed in your Wii U now, at which point the Pikmin will begin to unload all of the SD card contents and move it into the Wii System Memory on your Wii U's "Wii Mode". This part of the process will take longer than the last part. This took about 30-40 minutes for me.
Once this process is complete, your SD card will be erased, and your Wii U will go back to the Wii Mode home screen, with all of the purchases brought over. If you want to re-download any other content that wouldn't fit on your Wii System Memory when you initiated the transfer process, you can now do that from the Wii Shop Channel inside of Wii Mode.
2. What is "Wii Mode", really? How does it work?
Wii Mode is a fully virtualized Wii system inside of your Wii U, with all of the limitations and privileges therein. The Wii Mode system memory is limited to 512 MB, just like the Wii system memory is, so if you want to have your entire collection of N64 and WiiWare games available on your Wii U, you'll need to put them on an SD Card, just like you did on Wii. The SD Card menu is available on the Wii U's Wii Mode Menu, just like it is on Wii.
In other words, just like how your Wii became a GameCube when you put a GameCube disc in the disc slot, your Wii U becomes a Wii when you launch "Wii Mode." There are a few slight differences, however. The Wii System Settings are not accessible, only the data management settings. Although the Wii Shop channel is fully available, not all of the content is. The Netflix, Hulu Plus, and Youtube applications available on the Wii Shop Channel from your Wii are not available from your Wii U.
3. How long does the transfer take?
You can plan on it taking around an hour, but it will vary depending on how much content you plan on bringing over.
4. How do I access my WiiWare and VC games on Wii U?
Once you launch "Wii Mode" from the Wii U menu, you access them the same way you accessed them on Wii, either by launching the game channel, or opening up the SD Card menu and loading them from there.
5. Can I pick and choose the content to transfer?
No, you must bring over all of the following content, or none at all: Wii Software save data, WiiWare and save data, Virtual Console titles and save data, Add-on content, Wii Points, Wii Shop Channel activity, Mii characters.
6. What about my system-locked save files (Smash. Bros, Animal Crossing?)
These will come over to the Wii U, and will be locked in place there.
7. What doesn't copy over?
Not much. Netflix, Hulu Plus, Youtube, and, for some reason, LostWinds. A fix is currently in the works to bring LostWinds over to Wii U via the transfer process.
8. Will my Wii Points balance move over to Wii U?
9. What if I have Homebrew?
Obviously there are no guarantees but early reports seem to indicate that the transfer process is completely unaffected by the presence of the Homebrew Channel. I can confirm that this was the case for me. Though my Wii was wiped following the transfer, the Homebrew stayed and was left intact and still functional.
10. Do Wii games look any better on Wii U than they did on Wii?
Although the games will be upscaled to HD, that does not mean they are being rendered in HD. They will mostly look the same, but perhaps a little clearer as an HDMI signal is higher quality than component, and especially composite.
11. Can I use any Wii U accessories with Wii games?
No. Once you launch Wii Mode, any accessories (Pro controller, GamePad) that weren't compatible with your original Wii will not work with the system until you exit Wii Mode. This means that you can't play Virtual Console games on the GamePad, or use the Pro Controller for Super Smash Bros. Brawl.