Consistently downloads videos with no hassle. The companion app downloads faster than my browser does. There are several format options available for most videos. ADP formats put a QT code on the video if you don't buy the license, but it's not too big. You can still watch the video offline for free.
The plug-in seems to be improving. I have been using it for years, and up until recently, it would enable me to download any video for later viewing. Then, Youtube messed things up for a while, but the plug-in is working again!