I happen to tag all of my files with an ALBUMARTIST field, even when it's the same as ARTIST. From what I've gathered, this is not how most people tag their libraries. They tend to only use ALBUMARTIST when necessary, such as for 'Various Artists' compilations and for situations where an album has guest artists.
I was just wondering how Rockbox behaves when this field is empty on most tracks. When browsing Album Artists, does the list only include names that are explicitly in ALBUMARTIST tags, or when the library db is being built, does it set ALBUMARTIST=ARTIST when no ALBUMARTIST field is found?