The update to fix the bugs in Cave Story Wii is now available.  Some of the fixed bugs are:

Menu screen cleaned up: No longer "glitchy rotating selection" and instead a more tradtional 2D layout as expected.

Extra Modes are now locked untill conditions fullfilled.

Remixed music significantly improved. (Drumbeats make a huge difference!)

Sound mixing fixed. Raining EXP drops are no longer deafening to the ears.

Map screen no longer covers the entire screen with black. Instead it overlays the map on top of the play.

Script: "Examinate further" has been corrected to "Examine further"

You know you have the old version if the main menu has big panels that you spin around left to right.  The new version has a simple list of options. 
 
Worth mentioning (to people that don't power on their Wii very much) that you have to re-download the game to update it. Nothing automatic.  T_T 
If fact, it may ask you to delete the old version first. >_<;  Thankfully the Wii Shop menu has a button that takes you to data management...
Choose Wii Channels, choose the storage location, and delete Cave Story (it's over 200 blocks and the large icon should look like the title screen).
If you are looking at small icons that are 2 or 3 blocks, you are in the WRONG menu and might delete your saves!
They really could have improved on this from the Gamecube...