It would be very good for the ux if the last chosen folder and the tree would be saved and used as default value the next time when adding/selecting a new media item.
Otherwise in a nested folder structure it takes an huge amount of time to always open the folder structure to get to the same folder/item-view.
In this case also some "favorite folders" would be cool.
A very good similar UI/UX for this is Adobe´s Lightroom 4.
If you need more details, please let me know.