if we're flying US Air, we always stick to the 2 hour rule, because the terminal (B/C) has a smaller screening area. When we fly southwest, we usually will get there somewhere between 1.5 and 2 hours, since the screening for D/E is so much larger, we find we fly right through security most days. Like you, i'd rather not be rushed, but i don't like to sit at the gate for an hour either. So i base my timing off of which airline i'm flying.
HTH
ETA, we had a 7:00 AM Saturday flight and stayed at the Mariott at the airport last September, and will never do that again. It wasn't worth it. I had the points so our stay was free, but we barely got a wink of sleep, and honestly felt more rushed to get out of the room and over to the terminal that I ever have when we've taken a limo down from our house in the NE Philly suburbs (Montco). If you were planning on parking, I would also urge you to consider Pacifico's services, they do a great job getting you to the airport from their location, and will bring your car back to the airport for you when you arrive back home. We've found it much cheaper and easier than the longterm parking at PHL.