My kids both act kind of *weird* when they first start the meds. They get grumpy, sleepy, etc. It lasts for no more than 2 weeks. I *do* have more side effects with Adderall. It seems that they are much moodier on that drug than the others, so you need to watch that. Also, the fact that your son seemed drowsy is a good indication he truly has ADHD. As you know, the drugs are stimulants and in non-ADHD people they act like stimulants. If you have ADHD they act the opposite.
I did take Ritalin for about a week. When I got my dose high enough I felt jittery. It made me feel much more disorganized than usual so I figured I don't have ADHD and quit taking it.