Second visit even better than the first
Last stayed in 2005, before a minor expansion that brought their room count to 23. It's located in a small group of brick-faced row buildings that date back to who-knows-when. Two of the buildings still have fire marks on their second stories, evidence of the time prior to establishment of municipal fire departments when insurance companies had their own fire brigades. The fire mark confirmed the building owner's participation in the insurance program.
Yes, it's a charming boutique hotel in a great location. It's just off beautiful Rittenhouse Square and very close to upscale shopping as well as being near many great restaurants -- from high-end, well established places to the trendy, smaller spots. But it's the people at Rittenhouse 1715 that really make the difference. 
All of the staff go out of their way to be helpful. While enjoying the complimentary continental breakfast in their cheery basement cafe, I noticed a newspaper on a shelf and thought I'd read a bit while finishing the excellent coffee. It was the previous day's edition and, when the server realized that it wasn't the current paper, she raced upstairs to grab that day's edition and brought it to me. Just one example of any number of instances of exceptional service that I experienced during my 4-night stay.
Speaking of the breakfast in the cafe, while pastries, fruit and coffee/tea are included in the room rate, they also offer fresh squeezed juice ($4) and omelets, pancakes, waffles ($8 each), all prepared to order. The chairs and tables are French bistro-type and the china is attractively mismatched. Table linens, like the room bed linens and towels, are Frette.
My room was on the third (top) floor of the original building. Small but very attractive and well lit with three lamps -- all with 3-way bulbs-- and with a large, openable window looking south. While the daytime high temperature one day was 89, my room was comfortably cool although there was no individual in-room A/C adjustment. I could have adjusted the vent opening to moderate the cool air flow but I was very appreciative of the coolness. It was also a quiet, central air system, thankfully, not a noisy window unit. The heating equipment, which I never needed to use, did have individual controls.
If you enjoy smaller, more intimate properties that offer attractive and comfortable accommodations at a reasonable price, I think you will be pleased with Rittenhouse 1715.