I've used them for both my cruises. Note that they are almost entirely electronic, so you're really working with a website rather than an agent. Par for the course for a fee-less agency, really. (And you can still make changes on the Disney website as well, but payments have to be made through the agent.) You are technically assigned an agent, but the interaction I've found to be terse and cordial, but not overly friendly. That said, I prefer to do things on my own when I can, and if you're the same, you may prefer this. Emails I sent asking questions were responded to, maybe not as quickly as I like, but in a reasonable time frame. They are quick to communicate any changes to itineraries and the like.
My first cruise, there was an issue with the cruise transfers not having been handled properly. We got it sorted at the airport cruise check-in desk, but it was a bit nerve wracking. Considering it was our honeymoon, I could have done without the hassle. I haven't taken my second cruise yet, but I'm just assuming that's where the difficulty will be (if any), as we're going to have to change from a airport-port-airport to airport-port-resort once we know where we'll be staying for the land portion I'm adding.
You should note that cruises transferred to an agent will only get PARTIAL credit from the agent, as Disney now pays less to the agent for transfers. You will be pressured to cancel entirely and book directly with the agent. Make sure you get some sort of promise or guarantee that they'll get your room assignment back or the equivalent.
Supposedly,
Dreams Unlimited puts very nice (and practical) gift bags or baskets in your stateroom. We didn't get one on our honeymoon cruise, since it was likely before they started doing that. (We did, oddly, get a duplicate of a gift we ordered from
Disney Cruise Line, which we took to Guest Services and had delivered to another honeymooning couple, pixie-dusting it forward, as it were.) That said, they could stop doing those gifts at any time, so I wouldn't expect it.
I think the fact that despite issues with the transfers, we went with DU again should say a fair bit. Considering it costs you nothing and you effectively get "free" on-board credit, it should be fine.
" questions 
She/Du also gives a nice tote bag FILLED with goodies in each of our cabins, there are 6 of us so we have to have 2 cabins. Last year the totes were filled with small magnetic dry erase boards to put on the outside of your cabin door, deck of cards, crackers, fruit snacks, pen and paper, several highlighters [for the personal navigator] sun screen, gum, and several other things I can't think of right now. I do remember that none of the items duplicated any thing that we got with our Castaway Cay gifts. 
Hope this helps. 
