We are getting married in July and our planner just jumped in. And already it is worth it. It will take the stress off of me on the day, and leading up to it as well since I don't have to deal with organizing the vendors. As a self admitted control freak, it's taking me a bit to get used to but it is still a relief at the same time!
We did not have one as our wedding was very small (25 people) BUT, even with a smaller crowd with most being family, I still found myself and my husband were busy chatting it up with everyone so the head waiter from the catering company actually stepped up and would let me know if we were on schedule for dinner, if we were missing any items (she actually ran out and picked up coffee stir sticks!), honestly she really helped because I was so preoccupied. So, definitely think it's helpful to have another person there making sure things run along smoothly and on time so the bride and groom can enjoy the day and their guests!
My MOH is a wedding coordinator and has been a massive help and I know she will be so helpful day of. She has shared a lot of experiences with me about the weddings she has run and it sounds like it’s a very good idea to have one! The last thing you want on your wedding day is to be the first point of contact for problems, fires to be put out, complaints, etc. A coordinator will take all the heat for you so you can really sink in and enjoy your special day.
My husband and I hired one and omg were so glad we did. She dealt with all of the set up for our ceremony and reception. Dealt with any questions the vendors had since we were not at the venue before hand. She also dealt with anything that came up so that we didn't have to deal with and actually enjoy our day