My mom, the one who taught me most about baking, has recently been diagnosed with a gluten allergy, or intolerance if you will. She's not a celiac, so spelt flour in place of all purpose or other wheat flours is acceptable. Note: spelt flour DOES contain gluten, but it's amounts are almost insignificant in comparison to today's wheat flours. True celiacs, however, can not have any gluten, so spelt flour is unsuitable for them.
I've been dabbling with spelt flour in my baking recipes (thanks to the recommendation from my dear friend Betsy) as spelt flour is easier to digest. It yields a noticeably denser, though moister, product. I've found a very useful website that focuses on baking with spelt flour and how to alter recipes to use spelt flour in place of wheat based flours. Go on, have a peek: http://bake-with-spelt.com/ (download the .pdf).
In my coffee chocolate chip cookie recipe, I have used 1/2 AP flour and 1/2 Spelt flour with fantastic results. Give spelt flour a whirl and let me know how you like it in your recipes.