I tried again today and there is still no way to submit the reply. Am I the only person who is suffering this? How to other people submit a report?

There have been other users who have mentioned a problem with Submit Your Feedback page. See if you can load this page - http://input.mozilla.com/en-US/download#idea

Quite honestly, if you want a feature such as keeping a history of download speeds for downloaded files, you might want to look into an external download manager program. I seriously doubt that Firefox would ever get such a feature, and I have not heard of any plans for any enhancements to the download manager in the near future.

I can see the page (see attachment) but it says I have to have the latest version of Firefox... yet I am already running the latest version! I click on the link on the page, and it tells me I am running the latest version.

• frustrated*

That data is stored in downloads.sqlite, so a program or extension should be able to retrieve and show that data

CREATE TABLE moz_downloads (id INTEGER PRIMARY KEY, name TEXT, source TEXT, target TEXT, tempPath TEXT, startTime INTEGER, endTime INTEGER, state INTEGER, referrer TEXT, entityID TEXT, currBytes INTEGER NOT NULL DEFAULT 0, maxBytes INTEGER NOT NULL DEFAULT -1, mimeType TEXT, preferredApplication TEXT, preferredAction INTEGER NOT NULL DEFAULT 0, autoResume INTEGER NOT NULL DEFAULT 0)

You can see some details as a tooltip to the file type icon area in the download manager if you paste this code in the Code field in the "Firefox > Web Developer > Error Console" and click Evaluate.
The Download Manager window needs to be open and the tooltip is only applied to downloads that are currently visible.

const Cc=Components.classes, Ci=Components.interfaces;
var enumerator=Cc["@mozilla.org/appshell/window-mediator;1"].getService(Ci.nsIWindowMediator).getEnumerator(null);
while(enumerator.hasMoreElements()){var win=enumerator.getNext();
if(win.location=="chrome://mozapps/content/downloads/downloads.xul"){
var i,r=win.document.getElementById("downloadView").getElementsByTagName("richlistitem"),R,P,C='';
for(i=0;R=r[i];i++){
fP=R.getAttribute("path");
sT=parseInt(R.getAttribute("startTime"));
eT=parseInt(R.getAttribute("endTime"));
mB=parseInt(R.getAttribute("currBytes"));
sD=mB/(eT-sT);
tT=fP+"\nTotal Time: "+((eT-sT)/1E3)+" sec.\nDownload speed: "+sD.toFixed(3)+" KB/sec";
R.setAttribute("tooltiptext",tT);
if(R.getAttribute("selected")=="true"){C=tT;}
}
if(C)prompt(C,C);
}}

Sorry, but that means nothing to me. If they can't get a page to work, I won't bother to report issues or give feedback.