I travel extensively on business and therefore rack up some hefty cc bills, around 10k a month. I use a Bank One Card (formerly First USA) which does not charge me a fee and gives me points.

These points can be used on any airline which has been great when I want to fly friends to a city that my primary carrier (United) does not fly to (or does in a limited fashion). You can fly international and domestic and I have had no problems using the points during peak travel times. Its just comforting to know that I have a few hundred thousand miles that I can use on any airline if United can't come through for me. Yeah, I guess cash is nice but unless you spend serious bucks.....

One other nice thing is Bank One allows you to redeem points for cash cards at local stores like Home Depot. $100 gift cards are great ways to make friends!

Compared to a specific airlines credit card, these cards offer much more flexibility IMO.