I've been using the ASA online course. It comes with "comprehensive text book" (all the information written out), "test prep" (smaller chapters, basically meant as cliff notes for pretest review), and the video segments (1-2 hours long for each of the 7 or 8 full chapters). Personally, I'm a reader, so I haven't given the videos as much attention as the comprehensive. BUT, I've found the comprehensive to be really good, and the segments that I have watched have been pretty good!!
As a further plus for ASA, I thought I identified an error in the text and wrote them a quick note. I got a really knowledgable and polite response, in short order.
I talked to a CFI, and he said that ASA recently revamped their course and he felt it was now the best one out there. I can't comment on the other ones, but I can highly recommend the ASA Online Course! As a further plus, I believe that our own Bob Gardner contributed some of the writing and makes some appearances in the videos....