The only place I see for unstructured comments and notes is in the Captions Field. My thinking is that once I have text in the Captions, I can search on every instance of: "Dog" or "Cat" or "Uncle Frank" etc and create keywords accordingly. S, the unstructured text stays where it (in Captions field) is and stays unstructured but it suggest what key words I need to create and tells me which photos to apply them to.
The spotlight comments I'm interested in have about 30 keywords that appear over and over again spread out over roughly 900 to a 1,000 photos. I would happily do the same thing in LightRoom - if I could.
The easiest thing to do would be to start from scratch and write an import script that would take the files from the HD get the spotlight comments import the file into Aperture and write the spotlight comments into the caption field.
If for some reason you can't start from scratch because of prior work done in Aperture that you can't loose then its going to be a bit harder.
The biggest problem is that the actual master file location on the HD isn't available to you in a useable form. What I mean is, Aperture knows were the master is obviously, but the only two place you can get that information is either *File->Show in Finder* or *File->Locate->Referenced Files* nether one of which lends itself to being useable in a script.
Assuming that the current masters are referenced, because if they are managed I would stop right here, then the first thing I would try would be a script that went through the folders were the referenced masters are get each master in turn, get the comments and then have Aperture find that master and add the comments to it.
