I'm no expert by here's my experience with Adderall xr so far.... my script is for 2-20mg xr/day. I take one around 7 a.m. and one around 1 p.m. (I start feeling the rebound at 6 hours, so the doc upped the script from one to two a day). I've been on this dosage all summer. I get a mild headache usually, but not all the time, when the stuff is mostly out of my system. And, like you, I get grumpy and my ADD kicks in big-time on the rebound starting around 7 hours after taking the last dose.
I find with the xr it gives me a chance to experiment some....I experiment in when and how I administer the xr, but leave the daily dose at 40mg. For example, I might take 30 mg at 7 a.m. (open up a capsule, pour out half the itty bitty beads and toss them down my throat, chased with a whole capsule). Then at 1 p.m (or 2 or whenever) I take the remaining 10 mg. xr left in the capsule (which I've pinched at one end so I can tell it from the others). Or, some afternoons I'll take a half dose rather than a whole dose when I know I won't be in a high-output situation. btw...if find taking half a dose in the afternoon also eliminates any rebound effect in me, which is mild anyway because it is xr, not ir.
If I'm faced with a time of day when I really don't want a lot of adderall in my system (say I'm taking a late afternoon 15 mile bike ride (with hills!), when it's time for my second dose at 1 p.m. I'll minimize the "extended release" feature of the xr by chomping down on a capsule that has a half dose inside, so I get the equivalent of 10 mg. IR instead of 10 mg xr.
These "variations" are exceptions -- I find keeping things simple and not trying to use the medication for (as my psyc says) "performance demand management" is the way to go. Just get in the habit of taking the same dose that works the same way every day...trick is finding the right dose!
I found that the side effects on Adderall are very noticeable and very changeable during the first couple months, so yeah...you may see things settle down with time...I did!
I am also going to the Dr. on tuesday to see about switching from adderall xr to concerta. I am have noticed the benifical effects of the drug wearing decreasing and my husband says i act like "a hyperfocused non-emotional zombie"