"1. Will Append Object work with .dbo as well as with .x?; and"
"2. (not anything like as important) Will Append Object work with the
other file formats?"
Yes and yes for the simple reason that once Append Object works with .dbo files it will automatically work with anything else you can import. When you import an .x file (or any other format that's eventually supported) after loading the object is internally converted into .dbo format anyway. From that point on what applies to .dbo applies to your object.
Cheers,
Rich
"Gentlemen, we are about to short-circuit the Universe!"