Fructose is fruit sugar. On one hand, we're allowed to have fruit, so we are technically allowed to eat fructose (just like we're allowed to have the lactose, or milk sugar, in milk). On the other hand, a piece of fruit has a small amount of fructose, so I don't think you'd be able to normally consume the same amount of fructose in one piece of fruit that you would if you were using something like a cup of the distilled form for baking or whatever.
Personally, I'd stay away from it...but you could try a little and see if it gives you cravings. If you are looking for a natural sugar substitute, you might try stevia, or erithyritol (which sounds like a sugar alcohol, but is a natural one...Stonyfield farms just started using it in their organic yogurt and they're committed to not using any sugar replacements like aspartame).