In a world where credit card companies are all a bit slimy, Citibank at least tries to make a reputation by being less slimy than the others. All these companies have policies that border on unethical. It's become an accepted part of the business, and Citibank is no different in this respect. The difference is that they put a high value on customer service and will bend these policies and work with customers to keep them happy.
Of all the credit cards I've used, the Citibank AT&T Universal Platinum Card has the most helpful customer service staff. Any time I've had an issue, they have worked with me on it or fully explained why they could not.
My AT&T card is also my lowest interest rate card, despite several late payments over the years. While some credit card companies will raise your rate after a late payment and keep it high, Citibank keeps your rate low unless you present an actual credit risk to them.
The AT&T card has an excellent initial offer that remains a good deal over time. They're not pulling you in with a low interest rate just to gouge the money back out of you later.
This Mastercard does not have a rewards program, which is not a drawback in this case. With many cards, you end up paying for those rewards with higher interest rates or annual fees. The reward of the AT&T Universal Platinum card is that you save money on interest and fees and can purchase your own rewards. (I realize this isn't as fun.)
The Universal Card website is easy to use and convenient for scheduling payments online or paying at the last minute. You can get all your statements online if you'd like or have them sent by mail. There are no drawbacks to this card, really, aside from the drawbacks common to all credit cards. If you need a Mastercard and want to work with a company that values your business, the AT&T Universal Card is the way to go.