I use the terms interchangeably. The term bipolar is most often used as a descriptor, so the subheading on my blog says "I Hate Being Bipolar. It's AWESOME!" However, I've noticed that in more formal conversation, like when I'm talking with a new healthcare provider, I'll say "I have bipolar one disorder" rather than "I'm bipolar". Maybe it's my way of discouraging them from stigmatizing me...I've never really analyzed it to be honest.