I was also going to WDW last year during the time that Hurricane Wilma was threatening the area. Many friends and family urged us to cancel, but we decided to go, especially since it looked like the main part of the hurricane was going to miss Orlando.
I'm so glad we went! We only got the fringes of the storm (heavy winds about 60 mph, strong rain) for about 1/2 day. They closed the park for 1/2 day and let us in to MK and Epcot around 2:00 p.m. I felt very safe, and we never lost power. We had plenty of snacks in the room (since they didn't want us to walk from building to building when the storm was going through, and we couldn't get to the restaurants).
As another poster said, the weather cooled off considerably (it was uncomfortably hot and humid the day before the storm, then it was perfect the rest of our trip!). And the crowds seemed pretty light (because I think some people panicked and canceled their trips). More fun for us!
I really urge you to go! I would just plan to bring a couple of small flashlights in case of a power outage (but Disney hotels rarely lose power). Also, bring some small emergency ponchos to tuck in your pockets; the night before the storm there was a huge, torrential downpour and I was so glad I had a poncho! We still got pretty wet, but it helped a lot.