I have found Video DownloadHelper to be both easy to use and extremely versatile in the sense that one may customize it in a multitude of ways. For the technically minded there are a host of options, and for those with limited knowledge and experience there are still many easy choices eg. how many downloads at a time, default directories, appearance ~ choice of tools displayed etc. For those knowledgeable about video the choices go far beyond these. I have noted as well, the only time I have had a problem, the author of the software responded quickly to my concern and solved my difficulty. In summary, I think this software is excellent.

UPDATE: 5 years on and a recently revised format for VDH. I am really enjoying the new format. I use four or five different video download apps, each able to do something that the others can't. VDH is a vital part of the team.

2nd UPDATE: Have been using the new format for quite a while now and love the increased speed I am finding. One caution ~ on some sites the app occasionally offers two choices ~be careful to check the length as one is always 06 secs which you should obviously avoid.