How odd. I'd been reading a bit about stevia lately and stopped by my local health food store yesterday to buy some! (Not for my tea...for the dread evil of the too-strong office Folgers.)
I wasn't too keen on having 'sugar packets' everywhere, so I got a drop formulation. Undiluted, it does have a bit of an anise/licorice aftertaste. Diluted in coffee, however, I don't detect any aftertaste at all...though I've yet to decide if the foretaste is comparable to sugar. It is definitely sweet, though, and I found my first try quite acceptable.
The best part, though, was that I didn't have any crazy side effects from the stevia. With aspartame and saccharin, I get terrible headaches and about 30 min after consumption, I'm starving: never-eaten-in-your-life starving. I don't know why.
I don't believe stevia has any connection to salvia outside a semantic similarity, though. The plants of the Stevia genus (about 150 closely related species) are herbs related to sunflowers and native to Paraguay. Their leaves taste sweet. That's about it. Salvia divinorum, on the other hand, is related to sage and mint and is native to Southern Mexico. It's leaves have psychoactive properties and make you hallucinate--particularly with higher dosages. It is legal in most of the United States.