Yes, I have Primal Order (WotC first RPG product I believe) and it is one of the influences for my work. I don't think I have any of the other books - yet!
EDIT: DriveThru says I have already purchase them all - I guess I just haven't read them them yet (except Primal Order).
Glad we are thinking along the same lines then

Recommend the second book when it discusses Metaplanes that is really helpful; have a great rest of day.