We have some BOS overnights. I have also had the PWM layover, but not for a long time.

You will need a crashpad in PHL or be prepared to get hotels. I don't know how much reserves are flying at the moment. But if you are from BOS you should be able to commute in and out on the day of on a regular basis. Keep in mind DCA might be just as good, especially with the US Airways Shuttle, which goes more or less every hour to DCA, though I don't know when the latest flight is.

But if you have a crashpad near DCA it is a good base to be at.