I thought I'd share my bit of experience with stevia.
In looking for a way to add a touch of sweetness to some bottle conditioned beers without adding fermentable sugars I began researching artificial sweeteners. I learned that many wineries use stevia to sweeten dry wines, in fact many more than you'd imagine, and many which are award winning wines. It is stable, non-fermentable, is not supposed to cause any off flavors.
Having previously tried stevia in the powdered form, I was very surprised it was suggested for beer or wine since that powered stuff tasted pretty nasty, not much better than aspartame. It turns out that the powdered stuff is not actually pure stevia, and it is mixed with other artificial sweeteners and bulking agents to make it into a powder.
Still a bit skeptical, I purchased a bottle of some pure liquid stevia from amazon, and tried it out in a few situations and I have to say it is a very good substitute for sugar. It is not identical in flavor but I'd say it's 99% of the way there, and there are no noticeable off flavors to me. I have used it in some beers in moderation, I don't want sweet beers, I'm just trying to balance the flavors out a bit, and have really liked the results.
Tonight I used it in some chocolate cake I baked for Teresa, I made a recipe and split it in two. I made one recipe with sugar, and the other using the liquid stevia (2 tsp replaced 2 cups of sugar) I added an extra egg and 1/3 cup of yogurt to balance the missing bulk. Teresa and I tried both of the cakes next to each other and the agreed that the taste was almost identical. The main difference was the texture, the one with sugar seeming to have fluffed up more, that's not to say I preferred one texture over the other. The addition of the egg and yogurt was surely the cause, and by no means was my substitution scientific, so I'm sure there would be a better way to compensate for the textural difference.
Part of the secret of a success in life is to eat what you like and let the food fight it out inside.
-Mark Twain