LOL the cashier at the health food store just told me the same thing the other day about the first time she used stevia. It's very concentrated and if you use too much it tastes terrible. I get the little bottle with the eyedropper and use one or two drops in my coffee.
The other thing about stevia, even if you use the right amount and get the sweetness, the sugar aftertaste on the tongue is missing. For some things like coffee or yogurt this seems to work fine, but for other things like my popsicles, where I really want a sweet treat, I use a little xylitol too because it provides the aftertaste and the two together imitate sugar surprisingly well.
I'm not as convinced about the healthiness of xylitol, so I try to use it sparingly. Stevia on the other hand, I once saw a stevia plant in the herb section of a nursery and plucked a leaf and chewed on it - the sweetness is right there in the leaf.
Totally hear you about the sneak thing. That was my modus operandi for many years, as soon as everybody left the house I was raiding the kitchen - it was like a compulsion. I just said to someone else, I'm kind of surprised I'm doing as well as I am living alone. But in a weird way living alone takes away that dynamic.