Personally, I prefer booking myself and looking for discount codes here on the Dis or though my mousesavers emails. If you are not a planner and want to make reservations and forget about planning then going through a TA is the way to go. When you book with a TA that company owns your reservation so Disney will not discuss the reservation with you at all. If you want to change or add anything you needed to contact the TA and then wait for them to find the time to email you back. I used the company you are asking about in the past and they forgot about me when a discount came out and by the time I found out and called them about it I had to sweat it and wait for a cancelation and then I couldn't get the hotel I wanted because of their error. Had I booked it myself I would have been looking out for the discounts and applied it myself and gotten what I wanted.
HTH