I shoot in RAW and use Aperture 3 and I've been using the "Recovery" slider in the Exposure pane when I needed to recover blown highlights. That normally works well but occasionally I get a shot where this process does't recover the whole blown area, usually an area of sky given that I live in a sub-tropical location with some very nice bright sunlight. I'm not worried about trying to recover blown highlights in areas like actual light sources. The other day I came across a comment that pointed me to a different approach which seems to work better for me. It uses a feature of the "Curves" pane. Below the histogram in the curves pane is a drop down options box labelled "Range". The default setting is "Normal". Click on that and you'll find an option called "Extended". Select that and you'll find the original histogram now only occupies the left bottom quarter of the histogram display and you have a lot more space to the right of the original histogram. If you have blown highlights you will see the histogram extending into that new space and you will no longer see the histogram ending on the right by "climbing" the right side wall of the histogram area. The new area of histogram display to the right of the previous histogram area is the display for your blown highlight information. Move the white point slider to the right to include that extended area and you recover your blown highlights. In shots where I've exposed for shadow areas and skies have blown out badly as a result, I've been able to recover a bit more sky detail with this approach than by using the normal Recovery slider approach which sometimes doesn't recover all of the blown sky areas for me. Don't know if others are familiar with this technique. The pdf Aperture manual doesn't cover the extended range feature of the Curves pane particularly well and it was a comment in Scoppettuolo's "Aperture 3" published by Peachpit Press which indicated to me that the extended range feature offered an alternative to the use of the Recovery slider for recovering blown highlight information.