hangovers are caused by different things. the head pain is from the lining of your brain actually shrinking due to dehydration. often the nausia is cause by the fact that you had food in your stomach when you started drinking. the body will process the alcohol first and keep doing so at a more rapid rate, leaving the food in your belly to essentially go foul before it gets fully digested.
also, when you urunate a lot during drinking you piss out essential minerals, vitamines, ect, because your kidneys are in overdrive. the best way to beat a hangover is to prepare for it and drink water while you're drinking booze, make sure not to have a full steak dinner laying around in your stomach when you go at it, and take some aspirin before bed. actually, i think asprin and booze can kill your liver, some other things like tylenol or something might be better.
as for the chaser pills, many friends have tried them. they might work in some capacity, but if you slam down 20 beers and take some of those (you take them in proportion to the drinking, like another dose every six drinks) don't expect to wake up refreshed like you just had a relaxing 8 hours. i think they just negate some of the headache, maybe queisiness. one friend i knew took them, got shithoused, followed all the instructions, and felt worse the next day than he had in years. i found that after singificantly improving my diet that my hangovers were greatly reduced, but they also tend to be more severe when i'm in the best shape fitness wise.