So I really didn't think these would work, but my friend group has a yearly event that involves a LOT of drinking and I figured we could all try it on the off-chance it works for us. 4 people in the group (2 men, 2 women) elected to try it and all 4 reported back that their hangover symptoms were significantly less than they expected. After that party, we've all continued to use them and continued to have good results when drinking heavily.
It does NOT completely prevent hangover symptoms, but it takes it down to maybe 20% of what you probably would have experienced otherwise. To me, it's worth it, so I'm going to continue to buy and use these.