I always ask my favorite Chinese place to make my moo shu pork with some heat. If they don't, I usually add a healthy portion of siracha sauce. I like spicy food, so I want my moo shu pork to be a little spicy, too. I think it marries well with the plum sauce.
I'm not really a fan of the pancakes at all. I'd rather have my moo shu with crispy noodles. It's a texture thing, I guess. My version may not even be real moo shu anymore, but I like it.