Definately worth attending.
I attended several over a few years prior to applying and it really gave me something to talk about on my secondary when it asked "Why PCOM?".
Also, I had the opportunity to meet admissions staff and TRUST ME...they remember who you are.
I met these folks on several separate occasions and they didn't always remember my name, but my face stuck in their minds.
Come interview day, it wasn't "nice to meet you", but rather "hey, how have you been?".
Again...it really gives a good impression of the school and you get to see the campus. Plus the food is pretty good.
And, if y ou're in Philly, there's not excuses.
Good luck.