As someone who is partially based in Manhattan, EWR is just as viable option as LGA or JFK. This is a negative simply because I now have to do two searches for flights rather than one. For me it is mostly pricing out TATL business class flights.
For example Air France is now flying at least once a day to EWR and it is cheaper than JFK. But it might or might not be cheaper than UA or to EWR or BA to JFK, etc. I can see it all today with one simple search to NYC.