I keep forgetting that PersonalBrain is just a way to organize information sources (like documents, webpages, etc.) because I can see the possibility of so much more.
Right now, it is amazingly good at organizing individual data sources to each other, but not very good at associating the bits of data in the sources.
Once things like thought groups, and links from external apps and notes to individual thoughts in a brain are added, it will really be a "brain." Nobody thinks about the world at the level of entire documents; we piece together tiny bits of info - like sentence fragments, and combine them in unique ways.
When we can link small pieces of thoughts, notes and documents to other such pieces, the power of association will really open up.
PersonalBrain has replaced filesystem in my vocabulary, but is still waiting to be born as a "brain" with "thoughts"
Mac OS X 10.6