I have used the companion deal several times with great success. As another poster mentioned, it depends on your situation. I fly out of DFW on AA so most of the flights I want are available. I have used the Companion service 5 times in the last year 1/2 and only once did it not make sense and the rep even (to their credit) even acknowledged you could do better on your own at the time.

The other benefits definitely outweigh the cons of the concierge service. With the abundance of availability of internet, most feats can be done with a few clicks instead of dialing concierge. Just my .02 cents.