Me too. Tea is SO good for you! It has antioxidents and other good stuff in it, it's a mild diuretic, helps balance electrolytes, all kinds of stuff. Liquid health food! I brew my own tea for iced tea -- for Christmas I got a subscription to something called The Tao of Tea. They send me 4 cans of different varieties of loose-leaf tea every month. Since it would take the rest of my natural life to drink all that hot, I started making iced tea with it. Wonderful!
My mother's kidney doctor told her and I virtually the same thing (my mother, as many of you know, was hospitalized for water poisoning about a year ago, drinking only as much as a gallon or a little over daily). The specialist didn't even mention 1 glass of plain water. He said you can get all of your liquid from foods and/or beverages that contain water, no matter what else they contain (except alcoholic beverages in some, but not all circumstances). Yes, even sweeteners, artificial or natural and caffeine. Caffeine is a mild diuretic, but it still doesn't overshadow the hydrating effects of the water in colas, coffees, teas, energy drinks....
You should decide for yourself whether and to what degree you want to eliminate artificial sweeteners, colors, flavors, and preservatives from your diet, but they don't have any significant impact on your bodies use of the moisture in your foods and beverages - they all count.
It does get a little complicated. I drink decaf unsweetened green tea. Since you drink unsweetened anyway, I don't think a switch to decaf would be much of a stretch.