I am a pharmacy tech at a small pharmacy, aspiring pharmacist. So really you can't take my advice, but maybe I can try.
What I have noticed two things.
1) Drugs, especially used for psychological disorders, work for some people, and don't work with others.
2) Drug companies once they lose patents on drugs come out with new ones this some little "flare" so that doctors will prescribe it. That way they they can charge you more for a new drug and keep you from buying the generic.
Fun Fact: Shire pharmaceutical owns the patent on Adderall. Their patent is supposed to expire in 2009. Curiously Shire now has Vyvanse as an ADHD treatment.
I don't know a whole lot about the drugs themselves, but I understand how the drug companies work. Adderall goes generic, so they come out with Adderall XR (extended release, no generic), and now they will switch to Vyvanse.
My advice. If you medication works, stick with it. There is no sense in trying something new if you are content with what you have. You will also save money i am sure.
20 generic adderall = $~25
20 adderall = $~65
20 adderall XR = $~95
20-30 Vyvanese = $~95-130 (depending on # of mg)