I'm glad it's back but I'm not happy about how limited it is in functionality, now.

IF THE DEVELOPER HAS ANY SENSE, they would use a "native client" to do the filesystem stuff. (Like in External Application Button: https://addons.mozilla.org/en-US/firefox/addon/external-application/)

It leaves a mess all over the Firefox's internal download/browsing history instead of being self-contained. Completely worthless, try other solutions.