My guess of what's contributing to the light crowds:
1. Gas prices and uncertainty of the price going forward.
2. Underwelming re-vamp of Pirates. Let's face it there's nothing must see about the revamp of Pirates. It's a good revamp, but it's not good enough to draw in large crowds.
3. Thus, there's no must see thing this year. Last year, there was Space Mountain, Jungle Cruise, Astro Blasters, etc.