I've done this before, I'm an INFP. =) Works for me, I love being a wishy-washy mush. 

MBTI can be a good way to help flesh out your characters, too, along with the [url=http://www.enneagraminstitute.com/]Enneagram system.[/url] I usually classify my characters with both since the types don't match up to each other and that gives you a pretty unique profile to work with. For example, I'm a type 9 in the Enneagram even though most INFPs turn up as type 4s.