"i have been taking 30mg of vyvanse for one week now. it works great. the first day i could really feel the amphetamine and found it too strong and unpleasant but on day 2 i did not feel bad from it. it lasts long, probably 12-14 hours and is very smooth. the crash is relatively mild.
previously i have been on dexamphetamine ir 3x10mg/day for one month which worked really well, but i wanted something that is sustained released. before that i was on ritalin ir and la for over 15 years. the methylphenidate just did not work as well as it used to and i found the side effects more and more unpleasant. 
i can really recommend vyvanse so far. i am really calm from it and can focus very well on tasks. it also has less cardiac side effects than others."