The useful thing that Steve mentions is that, while they both come out of the idea of graphically mapping connections between ideas, PersonalBrain and MindManager are very different in how they work and in what activities they best support. MindManager is clearly an implementation of classic mind mapping concepts, where one has a central idea and expounds upon it by drawing links out from that central idea. PersonalBrain, on the other hand, is based on visualizing relationships between ideas, where there is not necessarily a single "central" thought. That said, there is a lot of crossover in how the tools can be used because of their core ability around mapping connections.
Steve also says that TheBrain has a new version of PersonalBrain, renamed TheBrain Desktop Edition, which will incorporate many of the aspects of their enterprise offering. Unfortunately, this new version is not yet available. But TheBrain's Harlan Hugh did acknowledge to the PersonalBrain YahooGroup what Steve Barth wrote in his article.