I've gotten in the habit of using evaporated cane juice (unrefined sugar) for baking. It imparts an actual caramelly flavor, rather than just the bland, slightly chemical sweetness of refined sugar. And, chemically, it doesn't seem to adversely affect the end product, meaning that it seems to do exactly what it's supposed to in concert with fat/moisture, etc.
The problem I have is that I've tried using it in a few "candy" recipes -- marshmallow (with disastrous results) and toffee (with merely disappointing results). It's possible that something else is the culprit (me, for example), although I take a very precise, scientific approach to confectionery and baking -- carefully weighing ingredients, using a precise thermometer, etc. I suspect it has to do with the chemical properties of the unrefined sugar. Can anyone enlighten me and provide rules of thumb for substitution?