I started using this app about a week ago and find it to be the best brainstorming app I've used. It is pricey, but it does work well. I used another app for numerous years and find XMind to be easier to use. It is quick and easy to brainstorm and it creates nice looking mind maps.

The one drawback is that the version of RTF that this app exports to is not compatible with iWork 08. It can be opened by NeoOffice though. This needs to be a priority for resolution, especially for the regular price. The developer is quick to respond and seems to really want to make this the best brainstorming/mind mapping app for the Mac.