Not all of Philly is grungy.
If you're looking to rent in/around Center City, look neighborhoods like Rittenhouse Square, Society Hill, Old City, Northern Liberties, South Street/Queen Village, and Washington Square West (the Gayborhood, but I wouldn't recommend some of the high rises in that area). If you don't mind looking outside Center City, look at Manayunk, Chestnut Hill (where I live) and Mt. Airy. Manayunk is awesome, lots of bars and restaurants. There are also some cool parts of West Philly, but I don't know that area too well other than University City.
The library and a bunch of museums are on the Ben Franklin Parkway. There are also some high rise apartment buildings there, and nearby is Kelly Drive, which is popular with joggers/bikers.
Macy's is the only department store. Walnut Street from Broad Street to Rittenhouse Square is like our version of Fifth Avenue or Rodeo Drive. The King of Prussia Mall is like Disney World for shoppers and isn't far.