I didnt take any of the courses, but I bought the Princeton DAT course materials and studied myself. I also had the Kaplan online stuff from a friend. I think both are pretty good.
The Princeton workbook, which reviews the sciences, are much better than the Kaplan stuff. The Princeton DAT review books are very similar to their MCAT books, but they added some topics such as ecology, plant, and animal stuff which are covered on the DAT. However, I thought the Kaplan practice tests were better.
I wouldnt take any of the courses, rather I would just buy the books and study on my own. The Princeton DAT books can be bought directly from Princeton for 400 or 500 I believe.
If you have anymore questions, let me know. I am also selling my Princeton stuff if you are interested.