I'm still slightly unclear on what this does, but if it allows you to mount your UMD as a mass storage device on your PC, I can think of another use for it - playing UMDs on your television.

Assuming there's a media player that can play the UMD video format, you could have your PC hooked up to the TV, and use it to play a UMD with your PSP connected.

Also, the recovery menu in the latest custom firmware already allows you to mount flash0 and flash1 writeable.