The Omni William Penn has two decent places to eat:
The Terrace Room is something you'd see in a bigger city: a large palm-tree filled room with a high ceiling and murals painted on the walls. This is a great work-lunch place with consistently good food, and excellent service. The waiters are top notch. The menu rotates fairly frequently, but I would recommend any of the pork/steak dishes that they're continually updating.
The Tap Room has more of a pub feel to it, with a lot of old wood, a nice little bar, and about 20 tables. Do yourself a favor and get the fish and chips at least once. They have a decent enough beer selection, and share a kitchen with the Terrace Room.