B ... On-Screen controls (like in Nintendo Channel)
Left ... Rewind
Right ... Fast Forward
Up ... Skip forward
Down ... Skip backward
Home ... Enter file selector / home menu
1 ... unused (OSD?)
2 ... unused (OSD?)
+/- ... Volume

While in file selector:
A - Select file or enter folder
B - Up one level
Home - Return to video
Up/Down - Move within file list
Left - Return to previous level (same as "parent directory") - (or up one filepage?)
Right - Move into directory (same as A, but not starting files) - (or down one filepage?)
1 ... unused (sorting/filtering?)
2 ... unused (sorting/filtering?)
+/- ... unused (GUI width?)

Things to remember:
Somewhat smooth scrolling in file list
Don't wait to scroll down in file list until you press down on the last visible entry
Info overlay (something like a TV station's "now playing" insert) for a few seconds after playing / in pause?