it all depends on what you want in your e-sword. Do you what bibles or word studies or commentaries or all three. The best way is download what you think you would like and read the module then keep it or delete it.
The resources in e-sword are generally from the previous Christian generation and so they are not in printed circulation today. Modern theology type books are written for todays language and new research process and are built from these previous generation books, we learn from the previous generation and build from there.
The "Must have modules" are YOUR must have.