I like Leslie as another confidant for Bruce and a connection to his parents (was she always a contemporary of Thomas Wayne or was that a retcon from Year Two/Batman the Animated Series?)
I dislike her though when her sole role in a story is just to complaining to Bruce/a member of the Bat-Family about the violent lifestyle and saying "what would your father think?" which happens a lot (especially when shes in the Azrael series)
Of course War Games obliterated her character, luckily they retconned that out of existence! It was a total betrayal of the character and her role as a Doctor