To be fair to corporate agents, they are limited by the rules set by the company that they are contracted to, usually price, and they do have their uses when things go pear shaped. In that case they have the great advantage of being connected to the booking systems while all you have is a flaky phone line, and the individual agents do seem to relish the challenge.
My personal experience includes hotel bookings being cancelled whilst I was en route, which is not a huge problem when arriving in a Canadian city in the afternoon but is not a lot of fun when arriving in Bangalore in the small hours; or getting a flight booking one month out which I should have noticed but when the date and day of the week are as expected I didn't check the month.
We have to use a corporate online system which is basically a screen scraper. This is notoriously slow and rarely shows the lower prices available on airline websites. Each line item on the travel req costs £25 so straight away for a simple trip with two flights and hotac they've made £75. Cooments have been made about the best use of employee time but I can search two or three airlines websites for the best flight before our system has finished its trawl. Hotel bookings are even worse. Unless you like poor quality hotels in rough parts of town or long commutes in strange cites more time is wasted getting more appropriate accomodation.
Are they a good deal? If you are in travel procument perhaps, as your ticket billings can be lower so that's
yourobjective met. From the company point of view, probably not, if all the manhour costs of travel are taken into account.