S.R.
We just got back from Orlando. We visited Universal Studios (both parks) we didnt purhcase the fast pass- I'm not sure if we were just plain lucky but frankly we didnt wait no longer than 10 minutes in line.
Disney world was a totally different story, some rides were about an hour wait, we also did Animal Kingdom and rides were about 30 to 45 minutes wait.
While we were at Disney World I literally felt not an extra soul can fit in the park, it was terribly crowded and it was really hard to move around. My sister was smart about getting on most of the rides, she waited for the parade to start. She immediately went on most of the rides without any wait. Right after the parade the rides went back to an hour wait.
Have Fun!