Concessions are horrible. Terminals are old. AirTrain is very slow and cramped (walking pace sometimes). It is connected to Amtrak/Nj Transit to Manhattan which is a bonus.
It's an amazing feat of engineering and science that they built an airport where every single terminal smells like greasy farts. Newark: I salute your stench.
Check your flight status before you leave for the airport and if available, sign-up for airline mobile apps or email alerts to keep up-to-speed on flight delays and changes.
United terminal has long security lines. Factor in time for security. Apparently parts of airport are under construction. However united refuses to open all the security counters to speed things.