Disney World is different than Disneyland. First, it is more spread out. Ride vehicles when you can. Things are bigger, but not necessarily better.
Pros
The castle is HUGE. It is as tall as you can get without having to put red warning lights at the top.
The train station has beautiful architecture, as well as Liberty Square and Phantom Manor.
Cons
They hire cheap labor, rarely can a maintenance person answer a question, let alone speak English.
The maintenance of the paint is sloppy. Disneyland looks like it is repainted by artists.
Overall Tips
Don't act like a tourist. If it rains, act like its not. Take a thin slicker if you want to stay somewhat dry.
See if you can borrow a walker. They are great for holding backpacks full of Subway sandwiches and drinks.
It rains a LOT, don't let it bother you. It provides you gorgeous clouds for some great photos.
Magic Kingdom
The train ride is great, lots of foliage and bridges. Just as you leave Main Street Station on the train, look for the bobcat on top of the cactus avoiding the wild pigs. This scene was transplanted from the original Nature's Wonderland ride at vintage Disneyland! Take the train to Frontierland station (good in that Disneyland no longer has one). Start there...
These are must see…
Frontierland
The Country Bear Jamboree has been ruined by a refab (no longer at Disneyland)
The Fort on Tom Sawyer's Island (not open at Disneyland)
Adventureland
Tiki Room is ruined, don't bother.
Take the Columbia around the Rivers of America. There are some classic scenes not found at Disneyland. A tad better, even.
Jungle Cruise is awesome, with extra stuff. Even a tad better than Disneyland. Really great if its raining!
The queue leading up to Pirates of the Caribbean is great, the actual ride is a very poor re-creation from Disneyland.
Climb through the Swiss Family Robinson Treehouse! (no longer at Disneyland) A real time machine for us old folk.
Liberty Square
Liberty Square is beautiful architecture, but nothing else.
Hall of Presidents is good, but Great Moments with Mr. Lincoln at Disneyland is better.
Phantom Manor has a great exterior, but an unimpressive interior.
Fantasyland
Most of the dark rides are carbon copies of Disneyland, however, Snow White is noticeably longer.
Tomorrowland
Don't miss Carousel of Progress (no longer at Disneyland)
Ride the Blueline in Tomorrowland, it is the closest you'll get to The People Mover that is now gone from Disneyland.
Avoid Stitch's Great Escape… waste of time.
Hollywood Studios
Worth a look, but there is a few don't miss and most to avoid.
Forget Fantasmic! It is a poor recreation of what they do at Disneyland. If you do see it, leave early to avoid the crowds.
If they still have the car stunt show, go see it! It is really fun. However, when you leave, run quickly to the Indiana Jones stunt show
The Indiana Jones stunt show is a lot of fun and they do a great job.
I like the model of the Imperial Walker in front of Star Tours. Great for pictures.
The Great Movie Ride is kinda fun. It was neat to see Indiana Jones with the Ark of the Covenant.
Pretty much everything else is meh…
EPCOT
Get ready to walk, and walk, and walk
Very disappointing knowing what Disney wanted to do, and what they did after he died.
In Canada, go watch the Circarama presentation. This is the closest you will get to "America The Beautiful" that used to be at Disneyland.
Don't bother Finding Nemo, leave him lost.
Mission Space is pretty fun.
Test Track is also pretty fun.
Animal Kingdom
Largely unimpressive, but there are a few gems.
The Kilimanjaro Ride can be fun. Ride it in the morning.
Dinoland… avoid like the plague.
Everest - DON'T MISS!! Best ride in Disney World. Set your mind to ride it at least TWICE!!
