Looks to be convenient when you want to modify units.
I would lose the sound effect though on opening the unit-dropdown. And possibly add buttons to the dropdown that allow you to go to the next/previous unit.
It could use some of the information from the imp.cfg as mouse-over effects to explain some of the values.
Most importantly though is the saving functionality, it's not clear at all how that works. Does it auto-save all the changes you make? And when you use 'save as' from the menu it still isn't clear if what you're saving because you don't start in the correct folder or are you given a suggested file-name? Do you need to save all files separately or does it save everything at once.
I found the 'save' button at the bottom, what would already help a lot is if that save gets a mouse over that tells you if you are saving just this single unit or to all units.
Even better would be to remove the current button and add two separate buttons, one that says 'save changes to current unit' and another that says 'save changes to all units'.
EDIT: And on the attributes view please make the list long enough to show all units without the need for scrolling. This sticks a bit too close to DK