[quote name='dmaul1114']It has 512 internal, but a good chunk of that is taken by the OS, channels that can't be deleted etc. Not to mention VC games etc.
SD cards up to 2GB can be used, but currently only for backing up stuff. You can't even load game saves directly off them--must copy them to the internal memory first.
So, as of now, the SD slot is mainly for pictures and music, and backing up save files, vc games etc.[/QUOTE]
Excite Truck lets you play songs from SD cards, so I would assume that the SD card can at least be accessed by software. Not sure if you can download stuff directly to an SD card, but technically, you should be able to download content to the system mem and then transfer it to an SD card and have it be used by the game. Although I'm not sure how the DRM for downloaded songs would work (could I copy a downloaded song to an SD card and use it on a different Wii?), so they may not allow you to do this.
For GHII songs on the 360, can you transfer songs from your HD to a mem card or something and then use them on a different 360?