We just returned from our first trip to Disney with our 20-month-old son. I read these boards a lot prior to coming, and I saw a lot of posts from people who, like me, were anxious about traveling with a young toddler. Therefore, I'm offering my experience with candor. Of course, each child is different, so please don't flame me if your experience was not the same. This is just one perspective. I know it sounds discouraging, but we really did have fun and are planning to return with him in a year or so. But the first 3-4 days were fraught with tears (his and mine), and I think he was generally overwhelmed by all of it and not really feeling the magic. If I had accepted a few truths beforehand, I think we could have made it a little easier on ourselves. So hopefully these points will help someone else:
1. Your child will behave at Disney like he does at home, so be prepared. Logically I knew this was true, but I was so excited for the Disney experience that I pretended he would be docile and just overwhelmed with joy to be doing whatever we wanted to do. Instead, I was upset and angry and embarassed when he consistently refused to get in his stroller at the parks without an epic struggle involving copious amounts of screeching and bucking like a bronco. He wanted to walk, but he can't endure all that yet, and besides, his version of "walking" was darting in and around the crowds at warp speed and trying to climb trash cans. This resulted in a lot of us carrying our 35-pound baby, which in turn exhausted us. This was stressful.
2. If your child doesn't nap during the day, you will have problems. we observed the mid-day retreat to the hotel for his regular nap, but the room just wasn't dark enough and he fought it and wouldn't go down. He did sleep briefly in the car coming and going. But he was not pleasant in the afternoon. Unfortunately, it was 35 degrees while we were there, so we couldn't have a relaxing pool afternoon.
3. Seriously consider a 1BR if you can afford it. We did this and it was money well spent with a very active boy who runs around every waking minute. The garden grocer delivery was also a good call. And the rental crib.
4. Some of the kids' rides are plain weird. Peter Pan incorporated dead pirates laying across the ship deck and even Winnie the Pooh has a strange psychadelic dream sequence that looks like Pooh ate some bad mushrooms. I don't understand this.
5. Some toddlers, like mine, cannot tolerate wait in line for more than 10 minutes. This means that even with expert fast pass usage, you might not get on more than 3 rides all day (and that's in low season).
6. Always carry a sippy cup. Some places, like the Hoop-de-doo Review (which he loved, by the way), don't even have lids. They served his milk in a giant glass bell jar. Not good.
7. Good stuff: he loved the actual rides when he was riding them. The carousel, Dumbo, Aladdin's carpets, Small World, Winnie the Pooh, it was all great. And he loved the character breakfast (or at least he didn't cry). He also loved the Hoop de Doo Review, I think because we were so close to the stage. We had some nice moments, but it wasn't easy.
OK, that's all I've got. Good luck to all you toddler travelers - have fun!
) I will need to go back to the hotel for a break from him. 
But then we got a routine and we learned that taking the bus with stroller(s) was not even close to the nightmare we read about
Another thing we learned was how much more there is to the parks then the rides. At the much slower baby/toddler pace you see A LOT more, I still remember our 1st trip to MK as a new family and my DW and I saying stuff like "I never knew there were shops down the little side street", how long has that barber shop been there?", "they have a restuarant in the castle?"...
i have yet to vist the World but i have seen videos. if i remember correctly that part is when Pooh is dreaming about honey, like a withdraw dream 
when I think about it. We will have two grandma's to help out so that is a big bonus.
