An example of Apple doing parallax right is the new iMac page:
http://www.apple.com/imac-with-retina/
At least the top image effect is very well done IMO and does a very good job conveying the central premise of the new iMac: looottts of pixels.
Having said that I really dislike what happens lower on the page where the iMac image stays pinned on the left and the descriptions scroll normally on the right. It's totally jarring to me. It seems unnatural that some of the contents would move with the scrollbar (as expected) and other significant elements would not. It immediately pulls me away from the content and leaves me trying to analyze what in the world is going on.
We experience parallax in the real world every day and are completely wired up to find it normal and expected. But real parallax involves objects at different distances. When you force objects that are in the same plane to move as if they were in different planes, you get the "funhouse" effect.
I suspect that like many other cute effects somebody will eventually do some serious AB tests and figure out that this kind of thing reduces conversions.