When baking what works well as a sugar substitute?
It's going to depend greatly on what you're baking.
Sugar serves several different purposes beyond just providing sweetness.  Besides sweetness:


tenderness by interrupting and minimizing gluten formation.  Sugar promotes spread in cookies
Retain moisture and extend keeping quality (in baking sugar is actually considered a "liquid" ingredient due to its hygroscopic qualities - the ability to pull moisture from it's surrounding atmosphere). 
Promotes browning and caramelizing
Assists in aeration and leavening (as in creaming butter and sugar to aerate the dough)
stabilizes egg whites
Provides food for yeast growth and fermentation


In some instances you might be able to use a syrup (honey, corn syrup, molasses, etc.) but not in all cases.  For instance the granular nature of sugar is necessary for aeration of cookies and cakes because the jagged edges create air pockets as they pass through the fat.

Syrups primarily serve the purposes of sweetening, browning, and moistening.  Honey could be used in muffins that are being made using the muffin method (aka two-bowl method) because this method would use a liquid fat (melted butter/oil) but not in the creaming method (producing a more cakelike structure from the creaming process).  When using syrups you have to account for the addtional moisture that they provide.
From:  "How Baking Works" (Paula Figoni)
"The National Honey Board recommneds the substitution for using honey in place of granulated sugar.  This accounts for both the amount of water in honey and for its intense sweetness:  use 1 pound honey in place of 1 pound granulated sugar; reduce water (or other liquid) in the formula (recipe) by 2.5-3 ounces."

Overall, when making substitutions of ingredients that are critical to the structural and eating qualities you probably will not be able to replicate the same results with the substitution.  In the end, it will often be a case of "what is the next best thing" and realizing there will be quality differences in the finished product.