My son just rode Buffalo-Albany-NYC on the Empire State Trail, and I joined him for Poughkeepsie-NYC. Here are a few of his notes and mine on what to look out for:
Clyde to Port Byron: the on-road section is a high-speed highway, but the shoulders are mostly nice and wide.
Inadequate trail signage in Utica and Rome - have a map or cue sheet handy. If you lose the trail, remember the interactive map on this website has a "Center map at my current location" feature (click "Edit Settings").
East of Utica: trail closure for construction; the on-road detour (maybe 5 miles) was not fun.
After the detour part, at Dyke Road, the trail still follows an on-road route with uncomfortably narrow shoulders to Frankfort.
Around Ilion there were "Trail Closed" signs, but no problem actually using the trail.
East of Little Falls, they used the wrong kind of gravel for about 4 miles, resulting in a miserably soft surface. Be prepared to work hard here, for maybe 4 miles. A local rider said the state has no intention to fix this - but maybe if they get enough complaints....
After the relative flatness of the Erie Canal, be ready to climb some hills coming out of Albany/Rensslear. Likewise hilly (but very scenic) on the on-road portion from Hudson to Kingston.
Kudos to
Leisure Ride Bike Rental on the south end of Poughkeepsie for setting me up with a nice ride so I could join my son for the last 100 miles of the trail. They are friendly and helpful and have a great selection, and located right on the trail.
We missed a turn in Brewster where the trail transitions to on-road. If your trail ends at a staircase, you've also missed the turn.
Southbound through Brewster, the on-road section was not well signed. Be sure to have a map or directions.
The Westchester County portion (Elmsford to Yonkers and beyond) goes through suburbia, but you will go miles without access to the local streets and services.
The on-road section just south of the Harlem River is well-signed, but you have to watch very closely for the Empire State Trail signs, as there are lots of turns and lots of signs everywhere.
For the love of God, do not try to use the portable restroom on the Hudson River section south of the George Washington Bridge.
The southern end of the Empire State Trail ("official" signs and markers) is about 1/10 mile before you actually get to Battery Park.
Bikes ARE allowed on the Staten Island Ferry (just past Battery), which is free and affords great views of the Statue of Liberty. Bikes ride in the lowest deck - workers will direct you.
Happy trails!