An express is only quicker if it stops where you want it to, rather than in the middle of Harlem. At about 11:30 at night.

/VOE

As for what to see in NY:

Top of the Empire State building
Macy's
Skating rink in Central Park
5th Ave
Walk round the Village
Tavern on Jane (8th Ave Jane St) for fantastic brunch
Staten Island ferry to go past the girl
Times Square
South Street Seaport

That should keep you fairly busy.