I find "mp3tag" much faster than using Media Monkey for tag editing.
Just picked up my car on Thursday and started playing round with the external drive last night. No problems playing "wma" or "m4a' files and showing artwork off external laptop HD. Plugged in my daughter classic ipod and only some of the artwork showed. My bet is that her tags need editing. The biggest problem is when pluging and unpluging the ex. laptop drive the file system seems to get corrupted and will not play after a couple times. I'll probably end up using the ipod or thumb drives.