The word integration is the most useful aspect, keeping it all within one window.

I really enjoy being able to receive comments and actual redline suggestions that I can review and weigh before deciding what to accept.

I use Spellbook for my legal practice and it makes my job a lot easier. I can do it a lot faster, and it provides a good reference to source regulations and statutes. I also appreciate the really good template boilerplate language, which I can include for various provisions and legal documents. It's helpful that the Spellbook system is able to cite to specific regulations, like IRS tax code, and check the legal requirements or the viability of the provisions I'm putting into an agreement or contract. The initial setup was really easy.