Before the birth, my husband was very skeptical about the whole doula thing. He asked me, "don't you want me to support you?" And he really was hurt that I felt I needed more support than him.
After the birth? My husband is the biggest advocate for doulas you've ever met. He was EXHAUSTED from supporting me through my 13 hour labor, and if it hadn't been for the doula to give him a break, I would have had to do all the pushing on my own. The midwives and doctors aren't going to be there the whole time, so it's nice to have someone who is.
We delivered in a hospital, and I would HIGHLY recommend getting a doula. The most important advice I can give you is to interview a bunch of different doulas to see which one you are the most comfortable with - doulas come with all sorts of philosophies and approaches, and you should find someone who you are really comfortable with. And find out what their backup plan is, should they not be able to be there for the birth (due to whatever issues that may come up, or if another client is in labor at the same time)