Great, yet with a new severe flaw Rated 3 out of 5 stars
Ever since I found about this addon that I've been using it actively, and it never gave me any issues. Up until Firefox 3.6.x. Once I updated to Firefox 4, v4.8.6 started to be a very serious memory hog, making FF memory usage jump to 250MB right at boot (typical values are around 150MB) and just ate memory at a constant pace, until it used up all available memory. I tested each and every addon installed, and found DownloadHelper was the culprit.
Bottomline is that with the addon disabled, FF once again had a regular memory consumption and even got slightly snappier. I'll turn the addon on only when needed and keep it disabled for the rest of the time.This is a great addon, and should have this issue fixed as soon as possible.
EDIT: When going from FF3.6.x to FF4, DownloadHelper's icon is missing, but is easily restored through the toolbar customization menu.