they work OKAY, but I was usually still left with some brown spots. And the water thing was kinda weird... I did feel like it eventually affected the texture of the top layer of the fruit.
So here's my new tried and true solution (I'm probably not the first person to do this so I don't think I can patent it):
To save the other half of an avocado, make sure you leave the seed in it. Most importantly, you want to limit the exposure of oxygen to the fruit and removing the seed creates another air pocket. I took some plastic wrap and pushed it gently against the exposed part of the fruit and seed, trying to form somewhat of a seal. Then I wrapped the entire half with another piece of fruit and put it in my refrigerator.
Voila! a day later and my avocado looks GOOD. It was especially good this morning mashed on my sprouted grain mini bagel and sprinkled with some pepper.