The biggest advantage of booking a cruise through a travel agent is personalized advice from a knowledgeable source. A good travel agent will discuss your vacation preferences, budget and other travel needs and suggest which cruises will be the best fit. He or she can help you arrange flights and pre- or post-cruise stays, recommend in-port excursions and help with any special arrangements (think celebrations onboard or making arrangements for dietary and medical concerns).
Perhaps one of the most important reasons for using a cruise specialist is the high level of customer service you will receive that you will not get when using an online service or even a non-focused travel agent. The right cruise travel agent will be able to answer all of your questions and guide you through essential steps.
The right travel agent, especially one who specializes in cruising, will give you access to experienced staff with extensive knowledge who can help you choose the right cruise and stateroom. They will be able to take care of all your specific requests. If they sound vague or cold, ditch them and find a company that is passionate about winning your business.