They keep their tour groups smaller and use brand-new shuttle buses (think rental-car shuttle). The tour guides are personable and professional. They claim it's the most comprehensive tour. I don't know if that's true, but it sure covered a lot of Manhattan in a short period of time. I took my parents on it, and they loved it and commented that it was a great way to start their trip to New York.
They cover all of the main sights, like the Statue of Liberty, Wall Street, World Trade Center Memorial, Empire State Building, South Street Seaport, etc.
Check it out at www.newyorkpartyshuttle.com.