People on this board always say that there is no need for bug repellent at WDW. I can say for a fact that there are bugs at WDW. As we all know, some people could stand in a swarm of mosquitoes and never get bit. There can be one mosquito within ten miles and I will get bit.
The mosquitoes are there. Mosquitoes tend to be found near water, wooded areas and around large areas of plant life. Most of the theme parks do not meet those qualifications, thus, no mosquitoes in the park, or so it seems. Also, people tend to stay on the move which makes it less likely to be bit. If, however, you set on a bench in a quiet area of one of the parks near water, you may very well get bitten. They are there.
You are more likely to get bit at a WDW resort than in the parks. The reason being that the resorts are much more overgrown with vegetation than the parks. Again, people don't hang around outside that much, so they don't tend to notice them. They are there.
While Disney does a wonderful job of keeping things under control, they can't totally control the bug population. This is a sub-tropical area. We have a lot of mosquitoes.
All this being said, if you are the type that mosquitoes like, bring the repellent. If you don't need it...great. Better to have it than end up miserable.