Why do you think the brightness was turned down? Have you ever tried to use a macbook in bright sunlight? It's unreadable. In fact I was surprised by how clear the macbook screen was so I'd guess they had the brightness jacked right up.
Cameras don't always accurately reflect what the human eye would see but an LCD backlight simply can't compete with bright sunlight. The Pixel Qi is effectively acting as a mirror for that light.
edit: this video from last June has a good comparison with the kindle and a transflective screen right at the start and a standard LCD touchscreen at 5:20
I didn't think that the MacBook was actually in direct light. In fact from the angles it actually seemed to be shilouetted. The one time I did try to use a MacBook in direct sunlight, I found that turning the brightness off completely sort of worked ok. But then I just got up and moved somewhere else in the shadows.
Cameras don't always accurately reflect what the human eye would see but an LCD backlight simply can't compete with bright sunlight. The Pixel Qi is effectively acting as a mirror for that light.
edit: this video from last June has a good comparison with the kindle and a transflective screen right at the start and a standard LCD touchscreen at 5:20
http://www.youtube.com/watch?v=oawX3wenxNc