Here's my answer: You SHOULD have a doula IF YOU want one.
I'm a certified birth doula. I love what I do. I work independently and meet with prospective couples before WE BOTH decide if we are a good match. Then we meet a few more times during the pregnancy to chat, go over birth plans, and get to know each other... with some couples, I do more meetings for breastfeeding and childbirth sessions (I'm also a LLL leader and a Lamaze-trained childbirth educator). My clients usually call me to their homes once they are in labor, but not ready to leave home (if they aren't having a homebirth). I stay with them from the time I am called till a couple hours after birth, so I provide a steady, constant, comforting presence... especially important in a hospital (or some birth centers) where shifts change, staff changes, etc. I provide encouragement, comfort measures, suggestions for positioning, etc, and usually spend most of my time helping Dad to help Mom. Some Dads are not comfortable in this position, though, so I step in where I am needed. No matter how much a dad may understand your wishes for a natural birth during the pregnancy, once he sees you in pain, he may want to "fix" things for you. A doula, experienced with childbirth and not so personally involved with you, can help you and your mate push past that place and move on with your wishes. Or, at times, I have helped a couple work through their feelings and thoughts and decide whether or not to accept some intervention they didn't expect to encounter (I don't, in any way, make decisions FOR people, but I can help them ask the questions that get the answers they need to make a truly INFORMED decision). I gofer ice, water, warm compresses, ice packs, snacks and juice, extra pillows, etc, etc, etc... Once the baby is born, I help to establish breastfeeding IF I AM NEEDED... sometimes Mama and baby just need to be left ALONE! Then, I help tidy up if needed and go home, available by phone till our postpartum meeting, sometime within the first 2 weeks--determined by mom & dad.
Now, personally, I have never had a doula. Weird? IDK. My labors are typically very short. My husband is very hands-on and super awesome. I have about 3 preferred laboring positions and prefer to actually birth my babies lying flat on my back (I know, I know, I can HEAR you all saying that's a horrible position for birth) because my babies come VERY fast and lying on my back helps me slow them down enough not to tear me wide open (but it is still typically two contractions from pushing urge to baby being born for me).
So, if you see a need for a doula in your situation, or if you just want a constant, comforting presence in a not-so-warm environment, I would highly recommend interviewing doulas in your area. You may find someone you really "click" with.