I have been messing around with FreeMind, since DThink 2.4.3 provides some integration. I found a wee issue - not sure if it is specific to my setup (Mac, Lion).
I like how the FreeMind quick viewer works. But sometimes am finding that FreeMind stalls when you try to open an mm FreeMind map from within DThink. Have to Force Quit FreeMind.
This particularly seems to happen if you move the mm file within the DThink database. If you leave it Indexed as an external file, then mostly it works.