This can keep all your archives in one place and continually add files from "add" folder. Or can decode to "new" folder. Or create new archive entirely from "new" folder. It's a lot easier to see the benefits when you have a lot of archives you are continually testing with various files (especially when the number of files becomes very large like with char.lgp).
Plus one folder can keep the original archives for you to use again without having to keep copy pasting from game root. This doesn't make ulgp any easier - it makes managing large edits to numerous lgps easier. And it does it without having to know the command line.
I'm not sure how useful this will be for people, but it's definitely been useful for me.