Worth riding - yes, once. Worth waiting for - not for long. Worth using a FP+ - only if you can't get (or for some reason can't ride) FoP.
We rode it last week because we couldn't get a FP+ for FoP on our first AK day. The ride is beautiful, but there's not much to it except the pretty scenery. And frankly, Pandora at night is so pretty that you'd be better off just wandering around after dark than you would waiting in line for Na'vi River. It's not fair to compare it in any way to FoP but that ride is amazing.