All those horrible audio and control problems have been fixed! Just go to Wii Shop Channel/WiiWare/Cave Story and click update, it's completely free! (If it's on your SD card, you have to delete it off the card first.)
The new music and graphics aren't as good as the old ones, thankfully you can switch back. At least it plays the same, though! Now my brother can finally play one of the best games ever!
