I've never seen any bugs at WDW either, but I take bug spray every time we go just in case.
The reason I do this is because I used to be an operating room nurse. We had a patient one time, a 5 y/o girl, who had been bitten on the back of the leg by something at WDW. She developed an abscess, it covered the entire back of her thigh, and we had to go in and cut it out. Bugs may be very rare at WDW, but the ones that do survive the spraying are evidently pretty vicious!!
Kaycee