I agree that he makes good videos. I only really watched them to get a better understanding of probability and statistics though. It really helped me with those two areas, but I can't really comment on any other topics.
He is very good as a supplementary resource as avery said.
He is not making those videos specifically for the purpose of DAT test takers... so its not quite as efficient as a primary source.
Although I do have to say that I knew absolutely nothing about ellipses so I watched his videos on them and now I know everything I need to know about them! lol.