Thank you VERY much. By using what you said, "(via About:Config - browser.download.useToolkitUI - True)", I can now see my download speeds again. :D

There's also a new extension to modify the drop-down panel. I haven't tried it myself, but the feature list includes:

• Rearranges the status line in the panel to include the download speed
• Increases the number of displayed download items to 10 instead of 3
• Reduces the height of non-active download entries (in both the panel and the Library view)
• [option] Disable the big green alert arrow that shows when starting and stopping downloads

Source: Download Panel Tweaks. There might be others, too.

Try setting a preference in about:config

   See --> http://kb.mozillazine.org/About:config
   Preference to set (see values below) --> browser.download.manager.retention
       0 (<- that is a zero) indicates that the download should be removed upon completion (of download)
       1 indicates that completed and canceled downloads should be removed on quit (when you quit or exit Firefox)
       2 indicates that downloads should never be removed automatically (default) 

Download history can now be managed in the Library window where you can also manage History and Bookmarks. You can open the Library window with

   Firefox button > History > Show All History (or History > Show All History on the Menu Bar) or CTRL+SHIFT+H
   Firefox button > Bookmarks > Show All Bookmarks (or Bookmarks > Show All Bookmarks on the Menu Bar) or CTRL+SHIFT+B
   click "Show All Downloads" at the bottom of the new interface (see below) 

Firefox 20 also has a new download interface. You can also use the old download window if you choose

   Information here --> http://www.ghacks.net/2012/04/18/firefoxs-new-download-internet-how-to-restore-the-old/

The browser.download.manager.retention pref doesn't have effect with the new Download Manager. If you use that then the pref is forced to true, because download history is considered as normal history.