I have used MindJet MindManager since 1997 with version 3.0 of the software. I am in project management and it is a trusted tool in my toolbox. I use it for writing meeting notes, presentations, brain storming, and even developing a project plan. It thinks the way that I do and it is very easy for people to follow along either on a projector on on a WebEx.
Note taking on very complex subjects. Think of typical meetings that can dart from one topic to another and back again, with traditional note taking this is very hard to do, with MindJet it all part of the process. I particularly like exporting my notes out to MS Word with the MindMap on the cover and a Table of Contents and then a full display of my notes in a hierarchy.
Brain storming . . . nothing comes close. Get a room with a projector and your team and you are ready to go without the hassle of some software and since it is visual it is easier for others to make additional associations.
Project Planning. Yes you could build out a full project plan and then visually see the Gantt chart created. Work with the teams to do a Work breakdown structure (WBS) and then assign tasks and duration and resources. For small 100 or so line projects, it works great.
At the time, 1997 there wasn't much out there. I had just learned of Mindmapping techniques from a partner of the consulting firm that I worked for. When I saw there was a digital version of mindmapping, I jumped on the opportunity. I even went to get certified in the product back in version 5 because I believe so strongly in it.
There are so many uses for MindJet MindManager, but I have to say it makes its home nicely in project management. When comparing against other products of its caliber, I would confirm the easy import/export and sync capability with standard MS products. Also, make sure that the product works on all the different platforms that you may use (e.g. iPad, PC, MAC, etc.).