The problem with Late Blight remedies is the only time you can positively prove how effective they are is when they fail. If you don't get Blight, it doesn't mean they worked. It could just mean the disease didn't find it's way to your garden. None of the remedies, even those that are supposedly organic, are without problems. They are all toxic in one way or another. Neem kills beneficial insects, copper kills earthworms etc. Organic doesn't mean non-poisonous. I personally would prefer to use nothing. I'm even willing to surrender part of my garden to the local rodents and bugs. They were here first and I'm willing to share. In the case of a disease that is as destructive as Late Blight, however, I have only two options, use non-organic remedies or stop eating tomatoes. (the ones you find in the supermarket are sure to have been treated with chlorothalonil so by resorting to store bought, you've accomplished nothing). Last year I used Serenade and Copper with limited success. This year I'm going to use Daconil. My State Extension Service and the USDA say it's safe and effective, so I'm going to give it a shot. I found this to be an interesting link. Check it and you can see what your risk of getting Late Blight is. You can zoom in to street level.
http://uspest.org/risk/tom_pot_map