The show is fun & everyone should see it at least once. It is not long, so you have to decide if its worth it for you if you are a late night/park closer person.
If you do go, consider what rides/what area of MK you plan to rush to first. If you plan to try to get 7 Dwarfs Mine Train first thing, Peter Pan, Space Mountain, etc then line up on the Right hand side of the entrance for a faster & more direct shot. If you buck the crowds and want to see Haunted Mansion, Pirates, Big Thunder Mtn first thing, then line up on the further Left hand side of the entrance. Either way, you will be looking up to watch the Welcome Show & the train with character entrance. Enjoy!