I am lucky to be only gluten free, but many of those who are also have to deal with being dairy and/or egg free as well. My brother was allergic to milk when he was little, and had to drink rice milk, and even now that he is past that allergy, he will only drink the rice milk. While I do not prefer the taste on its own, or in cereal, I would like to try it in some recipes that call for milk, so that I can make some more dairy free recipes. Also, most recipes can substitute regular milk out for dairy-free milk. I have actually used rice milk in my pancakes before, when I was out of my milk, and they tasted the exact same. I would never have known they were dairy free!
As for the egg-free part, I am sorry to say I do not have the answer. I know there are egg substitutes out there, but I could not say what the measurements are or anything.