Perhaps you've seen the ads for the "new" sugar substitute, Tuvia. The reality is the Stevia has been used as a sweetener for thousands of years. We've been enjoying the liquid form for a couple years as a way to reduce our intake of refined sugar. I've also had poor luck with the powder dissolving.
Since I (and my children) do notice the after-taste, we combine it with sugar or honey in our Kool-aid type beverages lemonade, and sweet tea. Many of the children also like the flavored liquid drops in their milk. For some, that's the only way they'll drink their cow-juice. I'll also use it 50/50 with sugar in some baked goods, like muffins.
It is expensive, but don't rule it out on that point. The bottles of flavored drops last over a year in the 'fridge, and the big bottle of plain lasts us about 6 months of almost daily use in gallon beverages.
The liquids are cheapest when purchased through a natural foods co-op, but can be found at places like Whole Foods. I'm currently buying though Amazon for some savings and convenience!