Found some bugs with the controls. Dunno how long they've been present, but i'll try to keep it organized since you said to report bugs here instead of Google Code.
GC/CC Multiple Controls per button (mentioned on the google code, I forgot to mention it's present on Classic Controller there, so here it is again)
Occurs on 2D Grid View only
X decreases rows AND opens CoverDownload, Y increases cover rows AND opens Details Menu
[Note: On Classic Controller, it's the other way around, X opens Details, Y opens covers, but X still decreases rows and Y still increases rows]
Fix: Increase/Decrease should be mapped to D-pad Up/Down on both GC Controller and Classic Controller
GC/CC Virtual Pointer not working for left/right arrow
Occurs on Carousel view only.
Pressing A on GC or Classic Controller while hovering the left/right arrows on Carousel view doesn't work.
[Note: Carousel should scroll left/right continuously when clicking on these arrows, as it does with the Wii remote's A button]
Fix: Idk, make the arrows work when you press A on CC/GC controllers
GC/CC left/right on d-pad behaviour not match wiimote behaviour (not sure if it's a bug, or if it's intentional, but I figured i'd mention it anyway.)
Occurs on 2D Grid and Carousel view.
Left/Right on D-pad scrolls left/right only once per press, whereas +/- on Wiimote scrolls continuously.
Fix: Dunno, maybe do nothing, maybe map continous scrolling to L/R and leave it alone on d-pad, or just make d-pad scroll continuously.
[Note: If you DO map it to L/R, don't forget to also make L/R scroll left/right regularly on the channel grid]