Hooray! This SC is a much needed link in the chain. It is ~1 mile from I-95 and ~1/2 mile from I-76, the two highways that serve the Philly area. It is very close to I-676, a 2 mile stretch of highway which connects 76 and 95. IMO $5 for an hour is a reasonable fee (less than 2 gallons of gas). Free would be better, but this isn't bad and the SC is just off I-676, so if you are using 76 and/or 95, it is less than a 2 mile detour. It's right on your way.
I have only one caveat; Philadelphia is a Parade crazy city! The local news station (KYW 1060) does a terrible job of warning of parades (pending or even in progress).
E.G., one summer Saturday morning several years ago at about 9:30 a.m. I exited I-676 at 22nd st (the exit you would likely use to get to the SC) and instantly found myself in gridlocked traffic. I know the area well so I eventually worked my way out of the traffic and headed south, opposite the direction of my destination. After almost an hour fighting bumper to bumper traffic, KYW radio FINALLY said "we have reports of heavy traffic in the Art Museum area due to the Hungarian parade." How Shadow Traffic could be oblivious to a scheduled parade and failed to forewarn drivers is beyond my comprehension. My 9 mile trip which usually takes 20-30 minutes ended up taking me 3 hours and almost 20 miles out of my way!
Parades are most always held on route 1 (Ben Franklin Pkwy) between the Art Museum area at the west end of the Pkwy and Broad Street in the center of Center City Philly. This essentially bifurcates the city. To get to the SC, you need to cross the Pkwy, but it is completely closed to all cross traffic during events such as parades so you can't cross it if you are approaching from the south, such as from I-676. So, if there is a parade, Presidential motorcade, Papal visit, etc. and you are on 95 or 76, you must exit NORTH of the Pkwy and wend your way through the city using local roads. It's confusing and can be daunting if you don't know your way around Philly and you are still likely to encounter some heavy traffic no matter what you choose as your detour.
Thanksgiving and July 4th are the very worst holidays for this type of activity and can affect traffic for a day or two before the actual holidays. But events like the Hungarian parade, Puerto Rican parade, and other lesser known celebrations can really ruin your day if you are not forewarned and have the bad luck to be planning to SC in Philly on that day. It's not like we have parades every weekend, but we have more than most cities. If you are passing through when there is an event, it could really screw you up badly if you get caught in the web.
Other than that, the location seems pretty good to me. Philly is fully developed and thickly settled so there are few good places to build a SC or anything else for that matter. I think they did about as good a job as possible in picking a location that serves both major freeways. It really should be open 24/7 (and may be). If not, that would be my only other complaint.