When we booked our very first WDW/DCL vacation back in late 2008, we used a TA. Due to my unfamiliarity with WDW and DCL and the complexity of everything -- 5 days at WDW for 4 of us pre-cruise, followed by a 7-night DCL cruise for 14 people, with multiple flight itineraries, DME, pre-cruise hotels, etc., etc. -- I thought a TA would be best equipped to handle it, and I was right. We chose a reputable, well-known agency that specialized in Disney, and got so lucky with our agent. She was a joy to work with and made everything so effortless. 9 years later, she has since moved on and started her own Disney-specific travel agency, and I still have her as a Facebook friend. Whenever anyone asks me for a recommendation for a Disney-specialist TA, she gets my ringing endorsement every time.
Nowadays, with sites like this, and my increased knowledge of my options, I usually book things myself, but I understand how overwhelming it is the first time.