Center City in general has held up fairly well in terms of values. What has changed is that there are fewer active buyers out there now, so if you're looking to buy you'll have plenty to choose from and not much competition. In Old City the projects that were finished several years ago are, for the most part, doing very well. They sold most of their units before the downturn and have been able to keep selling at a decent pace by emphasizing today's great interest rates and the recently-expired tax credits. A few projects suffered from bad timing, coming online just as the market turned down - those are still mostly empty and struggling, and should be avoided by all but the bravest buyers who don't mind dealing with a struggling condo building in order to snag a bargain.
Aside from condos, the market for single family rowhomes has remained strong, and there's less oversupply in that category.
I'm happy to talk more in depth about your particular situation if you'd like.
James Yoakum - Realtor, SFR
Brown McKinney Real Estate
1631 W. Cabot St.
Philadelphia, PA 19121
office: 215-825-2250 x.1002