I love the improvements Apple has made to Panther and feel that my workflow has been made easier already.
Another feature I would really like them to add is the find functionality in open dialogue boxes. It would be so nice to be able to browse to roughly where I remember a document being and then using Find to locate exactly where it is. I am using this more and more in the Finder but it would save even more time if it was right there in the open dialog.
Since they have rolled a bit more of the finder functionality into the open dialog already hopefully this wouldn't be too difficult for them to add.
Not sure if this would be needed for save dialogs but I guess it might help.
I would also like it if they would break recent places into a folder instead of being hidden away somewhere. Right now carbon and cocoa apps seem to have separate lists but I would prefer it if the recent places where in a folder which we could access from the sidebar.
An improvement which I have mentioned before is giving us easier access to the recent items of individual applications. I would like to have the list of recent items of an application available in its dock menu or contextual menu even when the app isn't running. It would make it easier to start an app with a recent item. Right now you have to start the app and then go to its Open Recent menu.
Finally let us put the trash in the side bar as well, I have managed to do it using shortcuts but I always end up with a standard folder with the name .Trash.