Meds: How much success to expect?

I only recently had the epiphany(thanks to this site and some others)  that all my husband's bizarre ways of thinking and doing things are down to his ADD.  He always said he had a little ADD-- but I did not understand Adult ADD well enough to realize the profound effect it can have on interpersonal relationships.

I have talked him into getting evaluated and hopefully treated. (He doesn't think the ADD is a big deal).

So-- presuming he is prescribed Adderall or something else, how effective can this be?  I read some posts that say it is like "night and day", others say it does nothing. 

I understand that progress also requires non-medical therapy for both partners.  But we are both emotionally mature people who can usually communicate (or attempt to communicate) rationally-- there is no screaming or abuse in our house.  (just a lot of frustration) My husband has also developed some good coping skills over the years-- I see that now.  So anyway the point is that although we may still need therapy, we're probably better off in that department than a lot of people.

I think what I really want to know is how high I dare get my hopes, if he goes on medication.