We used the Phlash during our one-day visit to Philadelphia after reading reviews online. First of all, the deal has changed slightly, it's still $2 a ride or you can buy 7 tickets for $10 at the Indepedence Visitor Center. You can't get the $5 'all day rider' style ticket anymore but you can still get money off your parking until 7pm (used to be 6pm). We paid $10 for all day parking and $10 for 7 tickets and it meant we could see everything we wanted in one day, albeit a flying visit!
The Phlash itself is great value when you compare it to the $30+ you will usually spend on trolley tours, and all the guides we came across were friendly and knowledgable. Really useful to get to the art museum and back if you don't have time for the walk, or do what we did and take the Phlash one way and walk back! Would highly recommend it as a cheap and cheerful way to get around.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.