We were there in 2005 for Hurricane Wilma (I think it was that one). They announced that the parks were going to be closed the following day and that the hotels would have activities planned for guests. We were switching hotels that day, from ASM to Boardwalk, so actually it was kind of nice to have a more leisurely day. The in hotel programming on TV was really nice, because they showed Disney movies all day (this is a feature that I wish they had during normal weather). The hurricane began moving in the night before and there was torrential rain and wind, but by the middle of the next day, they announced that Epcot and MGM (or DHS now) would be reopening for a couple of hours.
All in all, not so bad. Not really afraid to go back during Hurricane Season. Actually, we'll be down in 23 days!!!!!