Is say worth it. My first birth plan simply said "I will follow whatever the midwives recommend, but I would like to avoid having an epidural. If possible, I would like to use the birthing pool". As it was my first time, I didn't know what to expect so figured the midwives knew best - and they were great.... I used the birthing pool and no epidural.
My second was a full page and a bit plan! After my first I knew exactly what I did and didn't want. When we arrived at the local birthing centre (first was at a hospital though) and it was established that I was in labour, a midwife came in and sat down with us to go through my birthing plan. She read it all and asked questions as sort of "what if this" type of thing.
They followed my birthing plan to the letter and I was incredibly grateful. Even remembered that I'd said if I had birthed in the pool, I didn't want to try to get back into the bed to deliver the placenta and when I had to get out of the pool to check that everything was ok, they put mats etc on the ground to make me comfortable and not have to climb up.
My third (and definitely last) I don't remember much of. I had a birthing plan, but it was assumed that I was at the birthing centre again. They sent me over to a big hospital for no legitimate reason at all - the hospital asked why had I been sent there, I explained that my bp was 140/80 and it was just below their limit, and the mw rolled her eyes and said it wasn't the first time they'd sent people over when they actually fulfilled the criteria to stay there! FYI, my bp had been that in all 3 pregnancies, stayed the same all the way through and had not changed during labour with my first 2.
Anyway, I don't remember anyone reading my birth plan but I was in so much pain and a bit distracted they could have read war & peace and I wouldn't have spotted it! I'm guessing they did read it actually because I started asking for an epidural and the mw reminded me that I didn't want one and so I had pethadine - which did sweet fa and I still begged for the epi, so the mw asked my husband who said "she'll be fine, she doesn't want one really" (twat - he also got the gas and air taken off me when I was pushing because he decided I wasn't using it correctly..... I have never forgiven him for either of these things). The worst thing? Afterwards I had to go into theatre and they HAD to give me a spinal for that! Grrrrr........