The section between Lambertville, NJ and Port Jervis is quite nice. Take the path out of L'Ville (left onto path shortly after crossing the bridge). Assuming it hasn't been raining, it's even doable on road tires. And S.R. 29 is narrow and has no shoulder from the north end of L'Ville to the north end of Stockton (about 4 miles). After that, it opens up and there is a good shoulder until Frenchtown if you want to get off the path (but you probably won't).
Bull's Island, a few miles north of Stockton, is a great place to camp. But it's very popular during the weekend so try to hit it during the week. Weekends require a two-night stay unless you show up Saturday and there is a free spot. Try to get a walk-in site near the river. Then walk across the pedestrian bridge to Pennsylvania and have a beer at the Black Bass Hotel. The area is somewhat rural so if you are cooking, you will need buy groceries way back in New Hope, PA at the shopping center on Rte. 179). Long way to carry, but it's flat.
Heading north, Frenchtow is cute place. Not sure if the path goes all the way to Milford (where there is a good bakery) you will have to take the road. It's not the greatest, but it's the only way. Some traffic and marginal shoulder, but not death defying.
The way from Milford to Phillipsburg is charming. It follows the river past some pretty homes. At some points it's not even wide enough for two cars. Good thing there is little traffic. Just beware of the surface in places. Over the years there has been some serious flooding which has made it slightly bumpy in places. There will be some traffic in Phillipsburg, but then you will be back on quiant and secluded roads to Belvidere, where you cross to into PA and ride along the rover some more. I believe there is a campground along this stretch. Rte. 611 will probably have traffic, but I believe there is a good shoulder. Worthington State Forest across from Delaware Water Gap, PA is very nice. A reservation to camp might be needed. Just watch out for bears. Seriously. Most of the rest of the route to Pt. Jervis, NY is throught the Delaware Water Gap National Recreation Area. Very pretty. If you can, try to get to the Walpack Inn Rte. 615 for some of their famous black bread. It may be off route, though.
If you are feeling enegetic, before you get to Pt. Jervis, NY you will pass near High Point State Park in NJ. You can ride to the top and brag that you have ridden to the highest point in NJ--a whopping 1,800+ ft. It's actually a good climb as you are starting pretty much from sea level.
Hope this helps. Send me a private message if you would like more info.