On the relationship between doubt and faith

Many of you have already heard about the new book of Mother Teresa's writings. If not, one article is available at:

http://www.christianitytoday.com/ct/2007/augustweb-only/135-43.0.html

In spite of what the popular press is saying about her darkness, I marvel at how much faith she showed in following Jesus day after day even when she felt she was getting no feedback from Jesus.

How are others seeing this?