My travel is almost exclusively within the US on one airline (DL - only airline). My hotel and rental car are arranged through a TA generally (hotel choices vary greatly and generally terrible, but then I have no choice since most are comp'd rooms) and car is always from Hertz (elite status).

I tried TAs for travel. I tried 4 different companies within Jackson before I gave up. I would send them a list of sites I needed to be at for Sep 1-Dec 1 in early August, a second list for Feb 1-Jun 1 in early January, and a third list for Jun 1-Sep 1 in early May. I would ask for best upgradeable fares (since most were weekend travel and DL has this LU fare policy). No travel agent in Jackson got it completely right ever. There would be at least two trips going to the wrong places or correct places on the wrong dates. (Once, I wanted to go to LGA and was booked for LGW instead. Another time, I wanted to go to Orlando and was booked for ORY.) Then, I went with a recommended agent in Dallas with AmEx Business Travel. She managed to book a whole season's travel to the correct locations, but with trips starting in Jackson, MS, and terminating in DFW.

After that, I decided that I would rather do it on my own.