For our upcoming Christmas cruise, I had DU do my immediate families ressie and it went well (even though I was really confused, and was off by a year!). I booked a room for my in-laws directly with
DCL (since it was the weekend), then transferred it to DU and they linked the two. That's also gone fine. Tammy (Kaa) is our agent.
About 2 months later, I decided to add a couple of days at WDW to the trip and sent in a request for a room quote. That got lost in the system. About 10 days after I sent the request, I got an email from dreams saying that if they didn't receive confirmation, my room ressie would not be good anymore. I never got the original quote, so I didn't know to send confirmation. In the meantime, I had ended up renting points off the DVC rental board, so didn't need the ressies after all. I emailed the agent (I'm pretty sure it was Marla) and explained what had happened so that they could figure out what didn't work that time.
Just like any internet based system, there are bound to be slip ups. I think once you're actually in the system, DU is very knowledgable, particularly about DCL. They certainly know more than
AAA (who I booked the first cruise with!!!)