My TA is 1800 miles away. I speak to her via phone and email and it's no different than going down to the brick and mortar agency. It's actually better. I'll receive the best pricing even though these days it is the same as the cruise line's website BUT I almost always receive an on board credit or other perk.
She is the one who is doing the Cruisemates Thanksgiving Cruise and she was able to get EXCELLENT perks for this cruise. Pre-paid gratuities worth $150+, on board credit and a cocktail party. Not bad.
On my last cruise on Carnival Liberty I was supposed to receive an on board credit from her but Carnival messed up and I didn't receive it. I just dropped her a note wondering about it and she responded though she was on an Allure cruise and let me know what the problem was. She sent a check for the full on board credit amount as soon as she got home. Most TA's would have said: Sorry, I can discount your next cruise for that amount.
Just because an agent isn't right down the street doesn't mean they can't give you equal or better service than someone thousands of miles away.