DownThemAll is always a good option - but you are forcing end users to make a browser choice they may not want to use.
I personally use it with SeaMonkey browser with Linux Mint for my operating system.
You'll still have to keep track of what you have downloaded in the past from a topic - to avoid duplicates. But with a decent broadband connection - DownThemAll makes quick work of porn leeching.
Is DownThemAll compatible with my OS?
DownThemAll is a Mozilla Firefox, Seamonkey, Flock extension, which means that if your OS supports Firefox, then you can surely run dTa as well.
Will there be Google Chrome/Chromium/Safari 5 support anytime soon?
The short answer is “No”, mainly due to technical limitations of Chrome/Safari
http://www.downthemall.net/howto/faq/