Rated 5 out of 5 stars

it seems that

browser.download.useToolkitUI

doesn't do anything in newest firefox versions.

This review is for a previous version of the add-on (1.1.6).  This user has other reviews of this add-on.

Actually it does.

If it is enabled, you see a little progress bar inside 'download'-button and it turns into a green arrow, after a download is finished.

If this option is disabled, you won't see any progress bar or green arrow inside 'download'-button. Instead the classic downloads window appears once a download starts.

One "feature" got removed by Moz, because it was too buggy: 'displaying finished downloads inside library'.

I guess thats what you are referring to.