How would an assignment with the Defense Attache Office affect one's career?

A DAO position is one of those nominative type positions.  I believe that on the positive side, it shows job diversity.  Diversity within your career field is one of the top items that boards a looking at come promotion time.  Also, a position in a DAO could also provide POCs for follow on positions/job opportunities both in and out of uniform (especially in your career field).  I know two NCOs who are currently on DAO assignments.  The transition for them and their families was tough, but once they were settled and understood their jobs, it has become very rewarding for both of them.

I am also looking into the attaché program and from my readings and my CoC all I have been told as far as any type of career enhancement would be like most things how you perform in the job will dictate how you benefit from it. I am sure that there are side bar benefits depending on where you end up being assigned though.

Your in an intelligence collaborative network, so after a tour you will be registered inactive. You will or may not be able to apply for nonprofit jobs such as USAID, Peace Corps, etc...these pple are sensitive to those intelligence collaboration jobs. International Red Cross, or Red Crescent may be different though, as they take all kinds of people.

good luck