I tend to see spelt on a lot of stuff in organic/diet-sensitive parts of stores, in big letters suggesting they're advertising its presence. I know that it has more nutrients than wheat, but are there any downsides (aside from it being more expensive)?  I've tried cooking a few things (pancakes) with only spelt flour and haven't noticed any difference. Are there things I should adjust when working with spelt? 
In many cases, wheat and spelt flour can be used in the same way, but as spiceyokooko already mentioned, spelt gluten is not as stable as wheat gluten, making it allegedly more difficult to make e.g. fluffy yeast doughs. I usually don't have any problems with that either, but you should be careful not to work the dough too hard or too long.   Dietary issues are often not solved by replacing wheat with spelt. The species are closely related and if a person is allergic to wheat, chances are high that he is allergic to spelt as well. Especially people with coeliac disease should not eat spelt.  When it comes to organic cultivation, spelt is more pest resistant than wheat, making it easier to grow without the use of pesticides. Spelt thrives better in harsher climates than wheat, is not so picky about the soil, but has a lower yield per area than wheat. 