I know what a doula does but I've not used one. The midwives in Brussels were much more hands on and helpful than I believe they are in other countries and the post-natal support offered was such that I didn't feel like I needed anything extra. I guess I was one of the lucky ones!
I guess I don't really know what a doula does (have a very general idea). I don't think I would have wanted a doula, couldn't even stand the nurses near me. Certainly didn't want the husband near me. I just knew I had a job ahead of me and I usually work best on my own.
I'm studying to be a doula - so yes I know what one is. I didn't have one at my first birth, but my experience of having one at my second birth is what gave me the inspiration to become one. I think EVERY pregnant and birthing woman deserves a doula!
...all I know about doulas is that Sonya hired on...but Sonya is a fictional character. They may be a good idea if you can find somebody who is very much in touch with your hopes for the birth of your child.