About 10 years ago we had a B2B booked on the Fantasy, which we had booked with a DU agent. Since they specialized in Disney WDW as well we decided to book a week there at the end of our cruise using the same agent. I had never dealt with an agent for WDW before, I'm pretty knowledgeable in that area as we go several times a year. Then some family decided that they wanted to come and do the WDW part of our trip. They asked me to book everything and take care of the plans so I did it myself, leaving the DU agent out of the picture.
So the agent has our reservation and I have everyone else's. Then comes the
free dining offer. Absolutely no issues with changing everyone's reservations......except mine. I sent a request off to the agent but it was hours before I heard back from her. It was a mass email sent to all her clients, not addressed to me, and it stated that she was working on the free dinning and if a reservation was able to get it she would then contact us back directly. I'm sure she had a ton of reservations to worry about and I had only 4 however if I kept my reservation and had it in hand I would not have to wait and see if she was able to get me the FD before the rooms were all taken, I could have fixed it when I fixed the rest. It would have served me right if all my other family had free dining but I was not able to get it because I had given control of my reservation to an agent when there was nothing in it that I could not have done myself.
I will never give over my reservation to an agent again. For us there is no benefit. There is no bonus cash offer, its not cheaper, I don't have to wait for someone to 'get back to me' or wonder if I'm going to miss out on a deal. I can make my own fast passes and decide if I want to shuffle them around. Same with dinning, if I can't get the exact time I want then I can play around with options and not have to wait for emails between someone else and I before making up my mind. On a recent trip I wanted lunch for BOG but could not get a group of 6 in. I was able to make 4 different reservations to fit in our group but it took me several weeks of checking several times a day. I don't think many agents would be that dedicated to making that work for us. That's JMO.
I can see where an agent would be good for someone who is a first timer and doesn't know the ropes or for someone who is laid back and doesn't care as much but if you know what you want and can book it yourself then why lose control. We have never used an agent again and probably never will.
Again, JMO and just stating my one time experience with an agent. YMMV.