Since I work in Princeton, most of my use of the tow path comes from that area. The tow path is cool because it is realy flat and the scenery is awesome. It's cool when you go far enough in one direction, you are running through a trail with water on both sides. One side is the canal the other is Carnegi Lake. If you go in the other direction, you see trees hanging over from both sides.
When the seasons change you get a whole new view. Each season gives you a different look at the tow path.
One of the best thing about the tow path is it lets you know when winter is over. Generally if there is still snow and mud it's still winter(as far as trail running goes). Other than that, this is an awesome place to run in central Jersey with alot of access points.