When you began this thread you were asking specifically about RAW files that you needed to edit. Unfortunately, the nice iPhoto-PS-iPhoto workflow is broken with RAW files. iPhoto will allow you to open your RAW for editing in PS. The problem is that when you edit the RAW file it must be saved as another format: Adobe RAW, TIFF, JPEG, etc. Since there is no way to save the edited RAW as the same file format, there is no way for that saved file to link back to its original in your iPhoto Library. The method you described in your original post: Save AS to the Desktop, then import as a new original - is the only way to do it.
Your idea of using Bridge and editing the RAW files will work ONLY if you do not import the photos into iPhoto first. You could import using Image Capture to a folder outside of your iPhoto Library. Or if your camera/camera card mounts on the Desktop, just use the Finder to drag and drop them to a folder of your choice. You can safely use Bridge to browse any folders that are not inside your iPhoto library. You could open your RAW files from Bridge and edit them in PS. Again, editing the RAW files will create files in another file format. Don't let PS save your edited RAW files as Adobe RAW, because iPhoto won't import them (unless that was added in v7). Save those edits to another folder and when you're done, import that folder into iPhoto. You can preserve your RAW files in their original folder as a backup system of digital negatives, or burn them to DVD, or whatever.
I think those are the 2 basic choices you have. Neither is particularly smooth, but perhaps you'll get used to one.
Regards.