I never use the shuttle, always the skybridge as it is so convenient. Of course if you're traveling with more than just carryon the shuttle may be more convenient. As was mentioned up-thread if you arrive while the exec. lounge is open and you're Diamond/Gold then skip the lobby and go straight to the lounge for checkin.

Breakfast was good just arrive early for the best selection. Evening appetizers are also plentiful early on but don't expect a great selection in the last hour or so.

Staff in the lounge was very friendly. Made a day trip to NYC on the Acela and they arranged transportation to the Amtrak station AND a pickup as well.