Beavs, if it's any consolation to you, my husband was also diagnosed as an adult (30ish), and was on meds for a while, but no longer. He says the only thing he regrets about having it is not knowing sooner. He was very clueless socially, and once he was diagnosed, it was almost like seeing the world in color after having only known black and white. Even without meds, he said, he just could cope so much better knowing that his brain works differently than most people. He has been hugely successful in life, fortunately, and credits a good deal of that to his ADHD. I know a lot of people with it struggle to find the right place for themselves and life is very challenging for them.
Yes, adderall & ritalin take immediate effect and the effect wears off at the end of the day once it's out of your system. There's another class of meds that's used to treat ADD/ADHD that needs to build up in your body for about a month to see some effect (welbutrin is one example of that kind -- I've forgotten what the class of the drug is called).
I wasn't sure I wanted to post this, so I pm'ed Randi, but since others have opened up, I'll just share my son's experience here.... he has classic ADHD -- just cannot sit still. He is 9 now. When he was in first grade, the teacher pulled me aside and told me he was decoding words less well than the non-native english speaking kids. We had him diagnosed at that point (not that we didn't know, but we went through official testing). It took us more than a year to try meds -- we were very against it, but we finally had multiple doctors telling us any medication side effects would be less than the side effects of him not learning how to read. And, he was not learning how to read. I'd watch him try to look at a page in a book and I could just see that his eyes could not even focus on the words. Fast foward to now -- he is one of the most active readers in the class and doing really well in school (he's in 4th grade now). How differently this may have turned out if we hadn't tried.
Oh, just incidentally, his psychiatrist tells me that over the years of tracking kids, they have found that as adults, about 1/3 stay on meds, 1/3 use meds (ritalin/adderall) occasionally when they feel they need it (for tests or important work days), and 1/3 go off completely.
-Beth