As long as there s a size limit on Personal Books that can be uploaded, I don't use it - if you think about it, I sync my personal books manually now by using dropbox and Scan. If not all personal books can be uploaded and synced by Faithlife, I then have to support two ways of syncing personal books, plus there is no way to know which of my books have been uploaded and which have not (that I am aware of). My life gets more complicated by using Faithlife to upload and manage syncing.
So please Faithlife, if you want us to use this feature, complete it - remove the size limitation, give us a way to see what books have been uploaded, simplify deleting a personal book completely from ALL systems, and give us a way to remove books we have uploaded.