I think it is very limited keyboard support.  My Wii downloaded an update when I powered up my Wii to write the review.  I had not powered on my Wii for many months beforehand.  After the update and the reboot, I plugged in the same USB keyboard I use with my PS3.  Nothing.  It wouldn't even let me type in text fields.  I think it probably only works with a few specific brands.  Not sure why they couldn't write a simple universal driver like SOny did.  Lame effort, but then again it is Nintendo... so all of their efforts are lame.