I don't want a digital asset manager but rather I'm looking for a Mac app that has similar features of iPhoto/Picasa but let's me work at the file level instead of a separate database. I tried iPhoto '11 with the "Copy items to the iPhoto Library" unchecked which takes me most of the way there but what I would like is that when I change a photo, I want that change applied to the photo file instead of on a duplicate. And I don't want to Export to the file to see changes to my photos files. I have 1000s of photos already on my drive organized the way that I prefer and I would I would like the photo files on my drive to be the master copy. I was used the "Windows Live Photo Gallery" app which provided core photo management and editing capabilities. Is there something similar on the Mac?
There's Lyn which definitely allows you to work at the file level within your existing folder structure. However, it's editing capabilities seem quite sparse compared to something like Picasa or iPhoto. There's a free trial, so it might be worth a look.
Pixa looks like a new and fresh attempt at doing this well, and I am eager to throw out both iPhoto and Picasa.