When will I be able to download the upgraded version?

The update was made available in early December 2007.

When will the Wii consoles being sold in stores begin to come with the upgraded version pre-installed?

Consoles with the new version pre-installed started to ship around December 2007.

Is it possible to (visually) distinguish between the retail Wii consoles that have the old version and those that have the upgraded version?

No, this is not possible.

Which parts have been changed?

• It became possible to use photos of your choosing as the icon for the Photo Channel in the Channel Menu (Wii Menu).
• For the feature that allows you to play background music of your choosing that is saved on an SD card during slideshows, the supported format for audio data has changed from MP3 to AAC (the .m4a file extension). (With version 1.1, you will no longer be able to play audio data in MP3 format.)
• For the feature that allows you to play background music of your choosing that is saved on an SD card, it became possible to use random playback.