In keeping with the pulpish nature of Eberron, I'm thinking of Sarlona as being "the mysterious Orient" of the setting --- evil masterminds, exotic cultures, strange powers of mind and body, etc. And I like the fact that it can fill this role without being overtly Asian . . . keeps it fresh.
I am undecided. I really don't use the Quori much in my game due to my own inability to play them very well. So this book has less interest to me. However if I hear great things about it, then I may go out and pick it up.