Wouldn't be quite useful to be able to have something like a note or a sticker that you can stick to photos in Bridge.in my PS work flow I save at different stages, and being able to write what has been done to the photo without opening it would be very useful, IMHO!
You would want to create those notes with Photoshop's note tool, or to be able to add notes in Bridge?
Labels could help you halfway (color code "finished" or "in process" photo.
Using metadata could also be an idea, while the suggestion is implemented.
What I would really love would be being able to write them when retouching in PS, but being able to read them in Bridge later without having to launch PS . Label allows you to establish some codes (ie Finished), but you would need a lot of them to encode a portrait retouching session!