Yep - can't beat OnxMaps! Looked at aerial photos of a new elk hunting area this year months before arriving, marked waypoints, downloaded onto the GPS, and walked around like I had been there before. As someone else mentioned, it will also give you the names of the property owners and are pretty darn accurate!
Thought I would point out another source of updated aerial photography for PA. The USDA manages a program called National Agriculture Imagery Program (NAIP) that acquires aerials for the 48 states on 3 - 5 year cycles. Pennsylvania was photographed last year. You can use the USDA viewer to access these aerials and ones from later years. Please note that the NAIP aerials often have a pixel size of 1-meter (aerials in Google Earth / Maps are most often a pixel size of 1-foot) and that the aerials are taken in mid summer when nearly all crops are planted and growing, which is the purpose of the program. These same aerials will be served up on the PA spatial Data Access site at Penn State in the coming months, where you will be able to view and download them for use in GIS programs.
Link to the USDA Viewer (zoom in and the 2015 aerials will be the base map - use list on left side to see other aerials):