It just started about one week ago so there is likely not much significant data yet. I have seen people using the bikes. In fact, I saw two people riding the bikes during my morning walk to work. The other day I saw two people loading the baskets with groceries outside trader Joe's.
I live near the Art Museum and my walk/ride to/from work takes me by the main branch of the Library, the Barnes Museum, the Rodin Museum and Eastern State Penitentiary. There are some 5 docking stations on or near my usual route. Some of the station placements may seem odd if you don't know the particulars about an area. For example, there is a station at 20th & Fairmount and another one only 3 blocks away at 23rd & Fairmount. I suspect the former is aimed at luring Temple University students, many of whom live in the areas close to that corner, while the latter is aimed at tourists attracted to the bars and restaurants near 23rd & Fairmount, which is also only a few blocks from the Art Museum.
As I expected, I have seen some people riding on sidewalks, but too many.
I ride regularly to get to work, shop and go out to dinner. Personally, I cannot ever see myself using the service as I already have two bikes I can use for those purposes. The GF and I love late July and August in the city. Lots of folks go "down the shore." Riding in the city on a Saturday night during that period is wonderful. We'll ride to dinner then the movies then home.
I am curious if it will be ultimately be popular with residents of the city. I believe apartments in Philly are more spacious than in NYC, making it easier to own and store a bike safely here. If someone has the living space for a bike and thinks they might ride and least semi-regularly, they can go out and buy a beater for $125 or less.