Now that I've tried the traditional way of eating Greek mastic sweet-- a spoonful in a glass of water, licked -- what else can I do with it?

From The Foods of Greece, by Aglaia Kremezi:
Mastic: ...used to flavor breads, sweets, drinks, and ice creams, and also made into a natural chewing gum.
This is a beautiful cook book with a lot of ingredient information and cultural stories. I found it in my public library, and I was surprised to find how many of the recipes use mastic. Worth locating!

And I forgot to add above, you can make creamy ice cream with it as well.

Make pudding or rice pudding with it. Put it in cookies or even bread (the dried kind, ground up). Adds a nice creamy texture to the puddings.

I've never had it, so I'm afraid I can't help. But, I am curious as to what it tastes like. Can you describe it?