We just picked up PG... we played the first game with just my partner and I and we did it completely wrong as the rules go (didn't delete 8 random plants, played through all six sections, etc). We'll definitely try again.
My partner noticed that New York and Philadelphia are not connected -- that is, there is no pipeline with a connection cost for those cities. (I also noticed Savannah and Jacksonville fit this as well.) The artwork looks like they touch, but my partner claimed I could not connect Philadelphia to New York.