The great thing about mindmaps is that they provide an easy-to-follow visual reminder of the techniques and positions covered. For most this is quicker to review and easier to assimilate than text notes. You’re also able to get a birds-eye view of how everything is connected and (hopefully) improve your understanding those intricacies.
The downside is that without the source material (DVD, book, magazine, etc) they’re usefulness is greatly limited. Don’t get me wrong, they’re cool to look at but how much are you really getting out of it? So what can be done about that?