Also, by law, the prices are the same as the prices in area malls and department stores. Like another poster mentioned, there's no tax on clothing here and if you're in the market, might land a few good deals.
Definitely try the bars - O'Brien's is a great Irish pub - serves good food. Fat Tuesday has good cajun fare.
If you don't mind re-clearing security - you could walk a few hundred feet (or ride the moving walkway) to the Hyatt which has a nice bar and restaurant.
City of Bridges is a new restaurant outside security that has really good sandwiches.
A short cab ride (15 minutes) will take you to Robinson Towne Center - incredible shopping and restaurants there.
Enjoy your time at PIT - the best airport in PA