I do not know how I missed this, since Mythbusters is among my family’s favorite shows, but in one of the James Bond episodes, they took on the issue of the Gospel of Gin: Shaken or Stirred.
It warms my heart to see that once again, they get it right. (And Bond gets it wrong)
They leave out only two things here. One they should have. One they should not have. They rightly left out all mention of “bruising” things. I seriously doubt that gin bruises anyway. Some folks claim it is the vermouth that gets bruised, but I also doubt this. I’d suggest instead that people who shake Martinis are a careless and neglectful sort who probably let their vermouth go bad with age, and that’s where the ill flavor comes from.
What they should have addressed a bit deeper, because it is a serious problem for a lot of still learning cocktail-philes, is the issue of dilution. They do note that the problem with the shaken Martini is that it is too diluted. But they’d have done well to add a few seconds to the effect that some dilution is essential to every cocktail. Always remember, the ice is more than coolant. It is an ingredient. Too little is just as bad as too much.