Pros: Simple and convenient to configure and use. It's easy to choose where you want your videos to be downloaded, and it just downloads them in the background of the browser utilizing as much bandwidth as you and the destination server have available.

It works on youtube and most websites that host video clips, and it seems to be able to handle any size file as long as you have the space for it.

Cons: There are a couple of specially protected video formats that this seems to be unable to download, and it doesn't work with the big, paid streaming sites like Netflix or HBO (not that I expected it to).

It also requires the browser to be open while it downloads, so downloads will fail if you close the browser, but, since it's a browser add-on, this is to be expected.

Overall: I've been using it for over a year, and I highly recommend it.