@Kirby,
"On import, you can have Aperture leave files where they are (in whatever Finder folders you have set up), but still rename them."
Are you sure about this? I just tested in Aperture 3.3.1 with "Rename Original File" checked and it renames the "Original" file in the Aperture managed library upon import, but the source file in the folder that I imported from remains unchanged. Maybe I'm confused on what you wrote... are you saying this only works for referenced libraries? That's not what I want to do; I want managed libraries.
"What "safety" are you getting by using ExifRenamer to rename your files instead of Aperture?"
1) I want folders of all of my photos taken off camera to exist in a world without Aperture (or any other photo software). If Aperture kills my library, my first defense is to restore from one of my backups. However, the second defense would be to go back to my source folders and rebuild a library. I lost a couple of albums in iPhoto, but instead of restoring a backup, it was easier to just re-import from the source folders. In another situation, I had trashed (and purged) all of the images that weren't good images from an event. However, I was then asked by law enforcement to go through and see if I had any images of a suspect. I was then able to search through my source folders to see every shot I took (although didn't find the suspect).
2) I often want to get images off the camera an on my hard drive, and sometime far later in time will I want to import them into Aperture. In the meantime, I want to have them be named properly.
"But it is built-in: it's stamped in the EXIF. You are then taking some of the EXIF data and putting that in the file name, where, as data, it is less usable."
I'm not *removing* it from the EXIF data, I'm copying it to the filename where it can be better used on a system level across platforms. It's not a question of whether the filename is more useful than EXIF, it's a question of whether the filename can be more useful than IMG_0001.jpg. Here's an example, in the Finder, I can search for Blue Angels and find every single photo I've ever taken of the Blue Angels over the years...in seconds. If I'm looking for a particular image, I can then go to the year, month, day, and time and then open just a few photos to find the shot I'm looking for.
Ya, I know, that's what Aperture is for, and yes it's better at it.
Now look at the original post on this topic.
I can do the same search via Time Machine and restore a single image without even knowing when I may have deleted it in Aperture.