I know this thread is quite old but figured it wouldn't hurt say something. I suffer from chronic migraines and take Inderal and Trokendi for preventatives. I use Imitrex injections and Zanaflex for abortives.
Anyway! I'm a daily cannabis user and cannabis helps tremendously with my migraines and head pain. If I have a serious migraine, I can smoke and it decreases my pain by 50% and knocks out my nausea and vomiting. It doesn't stop the beastly-4-day migraines but it makes it more tolerable. For migraines that last longer then 3 days, I use Migranol (DHE 45 nasal spray) or my neurologist gives me a pack of Pred.
Overall, cannabis is a great arsenal against my migraines, I highly recommend it for those suffering with chronic migraines or cluster headaches.