First of all, i thank you very much for writing this program.
Here are some missing features that i will find very usefull.
1/ it would be nice, when we select a directory to have 2 little button (+-) in order to add or reduce the directory depth displayed for that directory.
2/ it would be nice to be able to hide a directory. It could be done via contextual menu. NB : freespace is a special case of that feature;
3/ Of course it could be nice to have hidden directory reappeard not only globaly, but also just under the selected directory.
4/ I did not find a simple level up. would be nice to have one.
I hope you will find those suggestion so nice that you were ready to develop them.
Anyway, thanks again.