Being a step-parent

I've heard from at least three different people in the last week that being a step-parent is hard. 

I think being a parent is hard.  I think being a kid with four parents and two homes is hard.  I really don't think being a stepmom is that much harder than being a mom.  (Once in a while it's a bit frustrating when someone listens to dad when they wouldn't listen to you but most of the time there's no difference.)  The difference is it's just a bit harder communicating among four parents and keeping consistent rules than it is between two, but I don't think I have it any harder than any of the other three parents! 

Now if someone would just show me where that Magic Guidebook to Parenting is ...