It tries to cross-connect when not asked for. It caused noscript to show a ton of cross-site requests. Also, even when not using Youtube at all, it somehow caused Firefox to fully load an entire CPU. I had to uninstall it.
Very good and flexible for downloads, but occasionally causes Firefox to freeze. I usually disable it after each use and re-enable when I want to download another.
There are some problems of using this after the recent update of Firefox version. It seems that this extension is slowing down YouTube (with a yellow bar error message)
