Triggered by the iPad touch interface, I started to use mindmapping for the first time in presentation design. Mindmapping is a process in which you jot down ideas and the connections between them quickly, and edit, clean up, and move things around later to get a more organized picture. I must say, it works a lot better than my previous approach: the pencil and a piece of paper. Especially since it is a lot harder to lose that piece of paper with your notes on it.
I purchased 2 iPad apps: iThoughtsHD and DropMind. iThoughtsHD was designed specifically for the iPad, and is the cheaper of the 2 ($10 versus $50 for DropMind). The DropMind app is an extension from an existing suite of desktop and web applications. The latter probably explains why it took a relatively long time for DropMind to come out with the app, a working iOS 4.2 version only appeared last week in the app store.
When reading my impressions remember that I am a light-weight mind mapper, just using it to structure ideas for a presentation. Reading around on the Internet it looks like mindmapping is a whole design approach taking things much further than I do.
For the purpose I use it for, iThoughtsHD works perfectly fine. The interface is straightforward and clean, and it is every easy to export mindmaps to PDF or sync them using a Dropbox account.
DropMind's user interface looks a little bit more sophisticated with more graphical options. When you buy the iPad app, they also offer a perpetual license for the desktop client, and the web app. You can exchange mindmaps between the applications. There is a wide arsenal of tools available that I did not yet have time for to explore. The one drawback I found is that when you export a map to PDF or JPG, the resolution seems to be very low (not an issue with iThoughtsHD). I think this is a bug, or maybe I did not configure the settings correctly).
The bottom line. For basic presentation outline scribbles, iThoughtsHD works just fine and costs a lot less than DropMind. Personally, I tend to favor the DropMind app, because of the cross-platform integration and the ability to start using some of the more sophisticated tools available once I have come up the learning curve (on the condition that they fix the resolution of the exported images).
Let me know your experience with mind mapping and mind mapping software.