There are many mind mapping products that can produce complex detailed ‘idea charts’. Xmind Free and FreePlane are just two such titles. But I like Scapple’s intuitive and casual freeform nature. I tend to do my broad, “Blue sky thinking” in Scapple, and then move on to a more formal, more rigid mapping tool to fill in the details.
If there is any improvement I’d like to see is the ability to export to the “.mm" file format. The OPML export is unsatisfactory in that it doesn’t really retain the linkages. Relationships are important to maintain, and it could save a great deal of time when I get to the stage where I want to add detail to my ideas. As near as I can tell, the (I assume) open source ".mm” file format is as close to a standardized file format as the industry has gotten.
I’m less concerned about importing “*.mm” files since I see Scapple as the start of the ideation workflow, but would certainly have no problems if it were able to import the ‘mm’ files.