I would say no unless there was some kind of interesting surgery going on.
At Planet Watch, once you get off the train, there is a petting zoo and a building where they perform surgeries with some minor animal exhibits included.
I can see some people finding value out of Planet Watch, but since you have to take the train to get to it and get back, and what is there is fine but not earth-shattering. I think most people will find it not rewarding enough for the time they invested. Nothing to see from the train either, really.
I think it's definitely a bummer that Lion King and Nemo aren't going. I don't care for Nemo, but Lion King's great and both shows help fill out the day too.