Works great in FF nightly 68.0a1! This addon is simple to configure and seems to "just work". It does what it's supposed to and doesn't seem to come with any fluff, ads, or anything not critical to the function. I wish more addons worked as well as this one.
As a test, I downloaded a driver from lenovo. I've got a 300mbit fiber connection, and lenovo has artificially limited downloads to 10Mbps. With this addon I downloaded the same driver at about 38Mbps. I tested with this url: https://download.lenovo.com/consumer/desktop/g7aud28us17.exe
Developer: If you happen to read this, please remove the 5 thread limit for downloads! I'd love to have it use 10 or more.