Biggest letdown was actually a tie between the Phantom Menace, and Kingdom of the Crystal Skull. I have seen Jedi in theaters at least 3 times and it is one of my favorite films, i really hate it when people claim revenge of the wooden actors is better than Jedi.
In fact the only time i have watched Jedi and wanted to smash something was in 2004 when George inserted Jar Jar and Hayden Skywalker, horrible in the worst kind of way.