The Philadelphia Marathon is my favorite east coast marathon, without a doubt. It was my first marathon in 2016, and running again in 2018 was like coming home. The expo is pretty good; lots of vendors, and the official Philadelphia Marathon branded gear is expansive and high quality. Bib pickup was fast, and the free tech shirt was nice!
Race morning can be tricky if you don't live in the city, but there's plenty of parking within a mile walk, so you just have to plan ahead (as in any big city!). I live 1/4 mile from the start line, so I may be a bit biased, but it's relatively easy to get through security, drop a bag, and get into your corral within 10-15 minutes.
The course itself is excellent; you run through historical sections of the city for the first 7 miles or so, and then climb up out of University City, past the zoo, and into West Fairmount Park. Crowd support out here can be lacking, but once you get down to MLK, around the Art Museum, and then to Kelly Drive, the crowds are huge. Kelly Drive is a ~10 mile out and back along the Schuylkill River. This can be windy, but beautiful! Aid stations are plentiful and the local running groups cheer like they know you personally.
The race finishes right past the Art Museum, and the crowds are huge and supportive. The finish area can be congested, but it's easy to get a snack and water and get out.
Overall, the Philadelphia Marathon is well organized, well supported, and well loved.