I think we can split this into two issues:
1. Folder modification times aren't quite right. The time isn't updated when a file is deleted, which is wrong, and it looks like there is already code there to update it on a new version of a file which is not working for me (and depending on what we decide here could be the wrong thing to do entirely).
2. Our users (and, I believe, most users) want to be able to tell at a glance whether there is anything new in a folder (or anywhere below it) without having to click through. They would be mostly interested in new files and new versions of existing files; I don't think they care too much about moved, renamed or even deleted files.
There is a "new" image which is supposed to indicate newness, but it is on all the time for everything right now. Even if it was working correctly it still wouldn't be too useful to us because it's based on "new within N days", and what we really want is "new since you last looked". But it's better than nothing, and my first pass on this issue could be just to make all of this work the way it's supposed to, which would be to make the folder modification times work like they do in UNIX, and have the new image show up for files which have changed and folders which contain changed files.
However... I believe that showing the "last modified" column to all users is going to be generally confusing. Especially if the folder time shows that something has changed, maybe a file was deleted, but the folder "new" image isn't showing because it's not really new content. So along with making it all work, I think it should be possible, by package parameter, to suppress the "last modified" column.
Thoughts? Is there a better way to approach this?
Secondly, I'd like to think about making the new image work on a per-user basis. This would also have to be parameterized since it's somewhat costly and not everyone needs it. Don, you implemented this on Sloanspace and you were worried about performance - how did it turn out in the end? I know it worked, but was it as expensive as you had feared?