I'm using the mp3j-ui widget.
In the 'More options' side there is a 'Playlist the tracks in alphabetical order' checkbox. I have this unchecked, but the playlist appears in alphabetical order.
There is an option to change the order of the playlist? For example to file date (it's the uploaded order) with the last file on top.
You can see this at the bottom of right sidebar http://rxi.cat/