Regarding checking to see if the files play okay with the metadata I put in them, and how much of the metadata displays in the player that is used, here are my own results so far:

VLC 2.0.4 (Linux, x86_64), Ogg: Plays fine, shows Artist, Title (no album art)
VLC 2.0.4, mp3: Shows Artist, Title, Album Art

Firefox 16 (Linux, x86_64) Ogg: Plays fine. No metadata. (No album art)

JuK, Ogg: plays fine, shows Artist, Title, Album (no Album art)

Amarok, Ogg: plays fine, shows Artist, Title, Album (no album art)

Dragon Player, Ogg: plays fine, shows Artist, Title, Album (no album art).

(kid3 shows the album art, so it's in there...)

Will be testing more and reporting later. Thanks!