"very smooth stimulant. effective for a little over 8 hours in my experience, not the 12 or 13 hours the manufacturer claims. i take 40mg and have for over a month and have no need to up the dose. i gave it 9/10 instead of 10/10 because it takes 2 to 3 hours to start working. but there is no crash and is incredibly smooth compared to ir adderall, focalin or ritalin. i also have an prescription for 10mg ir adderall to take at 5pm so after work i can study or work out or just be productive because by 5pm the vyvanse has totally worn off."