I have used and reused All Season's Travel for booking Disney cruises. I vowed I would never use a travel agency, but decided to try out All Season's on many recommendations. They specialize in Disney and keep up with all the latest discounts and specials. (I think look and navigation of their website stinks though!)
I research trips so much that I feel like I know more than the average travel agent, but I have learned a lot through the All Season's agents and their newsletter. For instance, they told me to do an onboard rebooking for a future cruise that wasn't out yet. Just book a random date as placeholder reservation. When the future trip opens for booking, they book it for me on release day at the onboard rebooking discounted price. (10% off, plus you get extra onboard credit.) I didn't know you could do that until they told me. Between the discount and the extra onboard credit, it saved me $700 on the cruise I have booked for this summer.
The other thing they are good about is rebooking your reservation if a lower rate becomes available. I don't know that they will necessarily give you better deal than any other good travel agent, but they are knowledgeable about discounts and specials.
Have you tried getting a quote from a few agents and comparing them?
http://www.allseastravel.com/