There is a feature in Aperture called “Show Focus Points” that creates an invisible overlay on the image and then indicates what focus point(s) was/were used to create the picture.  This has a certain potential for images that might not be as sharp as you would like.  They may not be sharp because the camera was not really focusing on what you thought it was, and this feature will let you see that.

Unfortunately, it does not appear to work with my cameras. I didn’t know whether Aperture just could not obtain the data or whether the data were not collected by the camera.  I posted to the flickr group, and found that the data really are recorded, but, apparently Aperture does not recognize them.  There is a program that can be run from inside Terminal that can access all the data.  The program is called exiftool.  The problem is, inside terminal, you must do it one image at a time.  Even at that, when I run it, I can’t find the focus point.  I can only find the focus mode.