Some interesting perspectives raised so far. I must say that I identify myself as being bipolar, although I only consider my bipolar disorder to be a very small part of myself. But instead of seeing the illness/disorder as only an disadvantage I also see it as a advantage in some ways.

Regarding the question stated in the title of the thread I think the difference is a matter of degree. For example, one might be creative as his/her normal self, but when you have 50 ideas then it definitely is the bipolar disorder speaking.