I disagree with blumebwaybaby, I've never seen the fireworks shot off from the shore, they are shot off from several floating barges in the middle of the river (either Hudson or East). This year we were on a boat in the middle of the east river and we watched the Macy's barges pass us and get anchored by Gantry Park.
Regarding the fireworks cruise make sure you book a reserved a seated cruise (not general entry) also ask about the extent of the "entertainment". We made sure NOT to book a cruise with a 5 - 6 hour non-stop DJ. Also due to mobility issues ask about the boarding process, we had to stand on the pier for 1.5 hours in the sun before boarding AND also due to mobility issues ask about how you are to view the fireworks. On our cruise we had reserved seats BUT the viewing was on the top open deck which was first come first serve standing room only and with 1,400 passengers and an open bar for 5 hours it got very aggressive when it came time to watch the fireworks. We had to stake our claim to an area of the roof deck 2.5 hours prior to the fireworks, we took turns holding down the fort. The cost for the cruise was $200/ per person, but for more money you can book a more intimate cruise with less standing and waiting.