My experience with a corporate travel agent (not AmEx) is that telling them exactly which flights you want, so they don't have to do much of a search, is great. And if they have an online tool, use it. The less work they have to do, the happier they are, and the happier you'll be. I've had a few arguments with my company's agency, but it's been a while since that happened (the last was my fight with them over why I wanted to fly the CO nonstop IAH-TYR flight that was $20 more than the AA flight to TYR via DFW ) and most of the time they just issue a ticket for what I requested online. But again, a lot of it depends on your company's policies, and the travel agent. But my experience is that 99% of the time when I tell them exactly what I want after doing my own research, that's what I get, no questions asked.