I would point out that, for a person who is accustomed to a certain level of pain (i.e. it happens more often than not, or at least more often than others), any given pain will be more tolerable than if a person who had never felt it before were to experience the same pain. I would actually estimate about 65-75% of a migraine for one who's never felt it before, just in comparison to a person who's used to it. But that may be me being too picky. It's been known to happen.

Having some experience with migraine sufferers (my mate once forgot how to speak during a migraine), I can say this for certain: You will probably be sensitive to light and sound, will feel as though your brain is trying to inflate to the point where it pops your skull, and certainly will not feel like doing anything physically-intensive.

Half a migraine (to me) would be somewhere between calling in sick to work, spending the rest of the day with an ice pack on your head and a steady supply of industrial-strength Ibuprofen, and trying to knock yourself unconscious just to make the pain stop.

That may be at the top end of the scale; I'm not sure, since I've never felt one before.