I just booked our July 2002 trip. I can't say that I'm not concerned about flying and about the high profile that WDW has, but if we stop living our lives, the terrorists have won. We live about 150 miles from NYC and heeded Mayor Giuliani's call for people to travel to there and "spend money". We went down the week-end of September 25th and were a bit nervous, but felt that we were doing our part to "return to normal". I feel the same way about booking my WDW trip.
So, I'd say, travel, take care and have fun...