What a treat!
Absolutely loved my stay at the Inn at Penn. I stayed there for 2 nights for a business trip with on site meetings. The staff was fantastic - super friendly and helpful. Each morning when I came back from my run, the bellman had a towel and a cold bottle of water for me. The front desk staff and the concierge were very helpful with recommendations and dealing with some business issues like sending faxes, etc.
The room was spacious with a very comfortable bed. The bathroom was very clean and modern with fantastic toiletries. The hotel is very environmentally conscious and the waste can is separated so you can recycle your papers, which was nice. The catering at the on site events was very good with lots of fresh, seasonal selections, including various healthy options. One of our breaks was catered with a Philadelphia theme - Tastycakes, soft pretzels, etc., which was cute. 
The hotel is the obvious choice if you need to be in West Philadelphia for anything near Penn or Drexel. It would even be a good choice if you needed to be in Center City and didn't mind being a little out of the center. It's a short cab ride or a 20 minute walk or so.