For people that dolwnload manually (and there are some) only having to download/unzip once then copy to the different path makes life easier especially as the number of Classic cients grow and no indication if downloaders will support one addon, multiple .toc checking.
The biggest bonus for me is I can have the addon under retail and setup symlinks to the other clients so I only have to make changes in one addon. -xxx.tocs with seperate .lua files for one or more versions or in-code version checking, you don't have to worry about where you're working or replicating changes as it all happens in the one addon
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