People, people, I know you're at the Convention Center, exhausted, and this is quick, easy, and reliable, and one place everyone can agree on and...
Believe me: the only excuse to go to a chain restaurant in Philadelphia is... uh... well, there isn't one. There are too many good restaurants here.
Go to Reading Terminal if it's open for lunch. There's enough variety there to satisfy your hunger and cultures to satisfy your soul.
For dinner nearby, go to Chinatown. On this site, you'll find suggestions from cheap to pricey (how much is your per diem on the expense account?) and from all cultures.
There are dozens of great restaurants near 12th and Arch. Walnut Street and Rittenhouse Square have several top-rated sites, like Striped Bass and Rouge. Funkier places, like the White Dog and Pod, can be found in University City, farther west down Walnut (buses go straight down Walnut).