I don't really notice a flavor change with Sun Crystals. I have a few teas that I'm using up that seem to have an "edge" to them that I don't like, so I use Sun Crystals with them to get rid of that bit of bitterness. (For example the 4 oz. pkg of Nilgiri Chamraj that my frugality is making me use up!) They also don't make things overwhelmingly sweet.
I had terrible side effects when I tried Splenda, but so far the Sun Crystals have been totally agreeable. No terrible headaches or stomach cramps. They are a little more expensive than Sweet 'n Low, but since I don't use them that often, it's worth it to pay a bit more.
Of course, we'll probably read reports soon about how bad Sun Crystals are, just like everything else! I like that they are made of only two ingredients, and I know what both of them are.