Regarind the market -Chester county as a whole is doing very well. The average days on market in Chester County right now is around 80 days, and according to a report that was released today, West Chester's average days on market is at about 80 days.
As far as asking, it depends on the type of home and exactly where you are looking as to how homes are done. I can tell you that the average list to sale price ratio in west chester is around 96% or a 4% decrease from list to sold price.
As far as asking for 15% off the asking price - that also depends on a lot of details - in general and with out knowing the details, my first reaction is that that is too much off the asking price, plus paying the closing costs.
If you would like further help on this, please feel free to contact me - Chris LaGarde, with the Cindy Dickerman Team of Keller Williams. I am a Buyer Specialist. You can contact me by going to http://cindydickerman.com/meet_chris_lagarde