I've had it work, but I've also had it not work.
I definitely have something wrong with the way I sleep, because once I'm out, I'm out. I didn't wake up to someone using a concrete saw and a jackhammer right outside my room. I shit you not! So sometimes I've fallen asleep after taking Adderall IR and it woke me up with a terrible headache, probably because it made me grind my teeth like hell when I was asleep. I think Adderall XR works better for the "alarm clock" type thing.
What I do is set my alarm an hour or two earlier then normal, and since I don't wake up to my alarm my GF wakes me up, I'll take it and fall back asleep. Hopefully, I'll wake up in two or three hours.